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Adaptive diversification of juvenile life histories in the chinook salmon, Oncorhynchus tshawytscha (Walbaum) Taylor, Eric Burke 1989

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ADAPTIVE DIVERSIFICATION OF JUVENILE LIFE HISTORIES IN THE CHINOOK SALMON, ONCORHYNCHUS TSHAWYTSCHA (WALBAUM) by ERIC BURKE TAYLOR B.Sc.(Hon.), University of B r i t i s h Columbia, 1981 M.Sc, University of B r i t i s h Columbia, 1984 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES (Department of Zoology) We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA May 1989 (c) E r i c Burke Taylor, 1989 In p resen t ing this thesis in partial fu l f i lment of t h e requ i remen ts f o r an advanced d e g r e e at the Univers i ty o f Brit ish C o l u m b i a , I agree that t h e Library shall make it f reely available f o r re ference and s tudy. I fu r ther agree that permiss ion f o r ex tens ive c o p y i n g of this thesis f o r scholar ly pu rposes may be g ran ted by t h e head o f m y d e p a r t m e n t , o r b y ' his o r her representat ives. It is u n d e r s t o o d that c o p y i n g o r pub l i ca t i on o f this thesis f o r f inancial gain shall n o t be a l l o w e d w i t h o u t m y w r i t t e n pe rmiss ion . D e p a r t m e n t o f Zoology.  The Univers i ty o f Brit ish C o l u m b i a Vancouver , Canada Date June 19, 1989 DE-6 (2/88) i i ABSTRACT Over i t s n a t i v e range i n the north P a c i f i c , the chinook salmon (Oncorhynchus tshawytscha (Walbaum)) e x h i b i t s two l i f e h i s t o r y p a t t e r n s d i s t i n g u i s h e d by the age at which j u v e n i l e s migrate from t h e i r n a t a l streams to the sea. Those that migrate seaward d u r i n g t h e i r f i r s t 3 months of stream r e s i d e n c e are "ocean-type" chinook, while those that migrate a f t e r 1 or more years i n freshwater are "stream-type" salmon. Both types may be found w i t h i n p o p u l a t i o n s but they a l s o d i s t i n g u i s h p o p u l a t i o n s dominated by one type or the ot h e r . Stream-type salmon were found to be more a g g r e s s i v e , had a stronger seasonal r h e o t a c t i c response, grew more sl o w l y , and were l e s s t o l e r a n t of s a l i n e water than ocean-type chinook. These d i f f e r e n c e s were present i n both w i l d - and l a b o r a t o r y -reared j u v e n i l e s and were concluded to be, a t l e a s t i n p a r t , g e n e t i c a l l y determined. C o n s i s t e n t d i f f e r e n c e s i n b e h a v i o u r a l and p h y s i o l o g i c a l t r a i t s were found i n comparisons among chinook p o p u l a t i o n s from d i f f e r e n t r i v e r systems, between p o p u l a t i o n s w i t h i n a r i v e r system, and among f a m i l i e s with d i f f e r e n t freshwater l i f e h i s t o r i e s from a s i n g l e p o p u l a t i o n . These phenotypic d i f f e r e n c e s were i n d i r e c t i o n s a p p r o p r i a t e f o r d i f f e r e n t d u r a t i o n s of freshwater r e s i d e n c e which i s c o n s i s t e n t with the idea that they represent a d a p t i v e d i v e r s i f i c a t i o n and components of f u n c t i o n a l l y important " s t r a t e g i e s " f o r a l t e r n a t i v e j u v e n i l e l i f e h i s t o r i e s . A geographic survey i n d i c a t e d that stream-type chinook o predominate i n i n t e r i o r streams south of 56 N, and i n both c o a s t a l and i n t e r i o r streams north of t h i s l a t i t u d e . Although o ocean-type salmon predominate i n c o a s t a l streams south of 56 N, there are a l s o many r i v e r s with both stream- and ocean-type p o p u l a t i o n s . Ocean-type p o p u l a t i o n s are c h a r a c t e r i z e d by e a r l i e r emergence i n areas of warmer a i r temperature and longer growing season, i n streams c l o s e to the sea. In l a b o r a t o r y stream environments, j u v e n i l e coho salmon s o c i a l l y dominated j u v e n i l e chinook salmon from a number of p o p u l a t i o n s . In nature, sympatric coho and chinook used d i f f e r e n t stream m i c r o h a b i t a t s , but a l l o p a t r i c chinook used m i c r o h a b i t a t s more s i m i l a r to those of coho. M a n i p u l a t i v e f i e l d experiments demonstrated that coho and chinook p r e f e r r e d d i f f e r e n t h a b i t a t types ("pools" and " r i f f l e s " r e s p e c t i v e l y ) , but that coho may be ab l e to d i s p l a c e chinook from "p o o l " h a b i t a t s . While g e n e t i c d i f f e r e n c e s i n h a b i t a t p r e f e r e n c e between coho and chinook probably minimize the i n f l u e n c e of coho on freshwater r e s i d e n c e behaviour of chinook, a g g r e s s i v e i n t e r a c t i o n with coho may promote e a r l y downstream m i g r a t i o n of chinook when a l t e r n a t i v e stream h a b i t a t s p r e f e r r e d by chinook are l a c k i n g . I t i s concluded t h a t : ( i ) stream- and ocean-type j u v e n i l e l i f e h i s t o r i e s a r e , at l e a s t i n p a r t , g e n e t i c a l l y based, ( i i ) i v stream- and ocean-type chinook represent f u n c t i o n a l d i v e r s i f i c a t i o n of j u v e n i l e phenotype r e s u l t i n g i n a l t e r n a t i v e l i f e h i s t o r y p a t t e r n s , ( i i i ) s e l e c t i o n f o r s i z e at m i g r a t i o n and time of m i g r a t i o n are major f a c t o r s d r i v i n g divergence i n j u v e n i l e l i f e h i s t o r y among chinook p o p u l a t i o n s ; environmental c o n t r o l v i a "growth o p p o r t u n i t y " or b e h a v i o u r a l e x c l u s i o n from stream h a b i t a t s by coho salmon i s of secondary importance, and ( i v ) the sympatric occurrence of stream- and ocean-type chinook i n many r i v e r systems i s probably the r e s u l t of repeated, independent episodes of div e r g e n c e . Thus, stream- and ocean-type salmon probably do not represent d i s t i n c t e v o l u t i o n a r y 1ineages. V TABLE OF CONTENTS ABSTRACT i i LIST OF TABLES ix LIST OF FIGURES x i i ACKNOWLEDGEMENTS X V i GENERAL INTRODUCTION . ..1 CHAPTER 1: Phenotypic c o r r e l a t e s of l i f e h i s t o r y v a r i a t i o n in j u v e n i l e chinook salmon 6 I n t r o d u c t i o n 6 1. Beha v i o u r a l and morphological v a r i a t i o n among p o p u l a t i o n s of newly-emerged chinook salmon f r y 10 Methods 10 Study p o p u l a t i o n s 10 C o l l e c t i o n and maintenance of w i l d f r y 13 Gamete c o l l e c t i o n and i n c u b a t i o n 13 A. Response of newly-emerged chinook f r y to water c u r r e n t 15 B. Aggress i v e behaviour of newly-emerged chinook f r y .17 C. Chinook f r y morphology 21 Re s u l t s 22 A. Response of newly-emerged f r y to water c u r r e n t ....22 B. Aggressive behaviour of newly-emerged chinook salmon f r y 26 C. Morphology and c o l o u r a t i o n 43 2. I n t e r - , i n t r a p o p u l a t i o n , and temporal v a r i a t i o n i n behaviour and growth of juvenile chinook salmon 48 Methods 48 Experimental animals 48 A. Inter-, intrapopulation, and temporal variation in rheotactic behaviour 50 B. Inter-, intrapopulation, and temporal variation in aggressive behaviour 51 C. Variation in growth rate 55 D. S t a t i s t i c a l analysis 55 Results 57 A. Inter-, intrapopulation, and temporal variation in rheotactic behaviour 57 B. Inter-, intrapopulation, and temporal v a r i a t i o n in aggressive behaviour 60 C. Variation in growth rate 67 Variation in aggressive behaviour and s a l i n i t y tolerance among families of juvenile chinook salmon 72 Methods 72 Experimental crosses 72 A. Variation in aggressive behaviour 76 B. Variation in s a l i n i t y tolerance 78 C. S t a t i s t i c a l analysis ...79 Results 80 A. Adult freshwater rearing l i f e history 80 B. Variation in aggressive behaviour 84 C. Variation in s a l i n i t y tolerance 89 1. Effects of size on s a l i n i t y tolerance 89 v i i 2. V a r i a t i o n i n weight l o s s and s u r v i v a l 92 D. C o r r e l a t i o n s among v a r i a b l e s 98 D i s c u s s i o n 100 CHAPTER 2: Geographic v a r i a t i o n i n , and environmental c o r r e l a t e s o f , j u v e n i l e chinook salmon l i f e h i s t o r y ....115 I n t r o d u c t i o n 115 1. Geographic d i s t r i b u t i o n of chinook salmon and v a r i a t i o n i n l i f e h i s t o r y 118 Methods .118 Geographic d i s t r i b u t i o n of chinook salmon 120 Geographic v a r i a t i o n i n j u v e n i l e l i f e h i s t o r y 124 2. Environmental c o r r e l a t e s of v a r i a t i o n i n j u v e n i l e chinook l i f e h i s t o r y 149 Methods 149 R e s u l t s 156 D i s c u s s i o n 160 CHAPTER 3: Beha v i o u r a l i n t e r a c t i o n between j u v e n i l e coho and chinook salmon and chinook l i f e h i s t o r y 172 I n t r o d u c t i o n 172 1. S o c i a l i n t e r a c t i o n between j u v e n i l e chinook and coho salmon 176 Methods 176 Be h a v i o u r a l o b s e r v a t i o n s 176 S t a t i s t i c a l a n a l y s i s 177 R e s u l t s 177 2. M i c r o h a b i t a t use by j u v e n i l e chinook salmon i n a l l o p a t r y and sympatry with coho salmon 181 v i i i M e t h o d s 181 S t a t i s t i c a l a n a l y s i s 184 R e s u l t s 185 3. E x p e r i m e n t a l i n t r o d u c t i o n s o f j u v e n i l e c o h o a nd c h i n o o k s a l m o n 197 M e t h o d s 197 E x p e r i m e n t a l a n i m a l s 197 E x p e r i m e n t a l f a c i l i t y 197 E x p e r i m e n t a l d e s i g n a n d p r o t o c o l 201 S t a t i s t i c a l a n a l y s i s 209 R e s u l t s 210 I n i t i a l b e h a v i o u r 210 E m i g r a t i o n f r o m t h e c h a n n e l 210 H a b i t a t u s e . . .213 D i s c u s s i o n 223 CHAPTER 4: GENERAL DISCUSSION 233 LITERATURE CITED 245 LIST OF TABLES Table 1. A g g r e s s i v e behaviours recorded f o r chinook salmon i n the study .. . 19 Table 2. Net movement scores f o r newly-emerged w i l d chinook salmon f r y 23 Table 3. Net movement scores f o r newly-emerged, l a b o r a t o r y -reared chinook salmon f r y 25 Table 4. P r i n c i p a l component c o e f f i c i e n t s d e r i v e d from MIS b e h a v i o u r a l data 27 Table 5. Component c o e f f i c i e n t s d e r i v e d from p r i n c i p a l components a n a l y s i s of stream tank b e h a v i o u r a l data 31 Table 6. Component c o e f f i c i e n t s d e r i v e d from p r i n c i p a l components a n a l y s i s of MIS b e h a v i o u r a l data of l a b o r a t o r y - r e a r e d chinook f r y ...35 Table 7. Component c o e f f i c i e n t s d e r i v e d from p r i n c i p a l components a n a l y s i s of stream tank b e h a v i o u r a l data f o r l a b o r a t o r y - r e a r e d chinook f r y ...39 Table 8. M o r p h o l o g i c a l comparison of w i l d - r e a r e d , newly-emerged chinook salmon f r y 44 Table 9. M o r p h o l o g i c a l comparison of l a b o r a t o r y - r e a r e d , newly-emerged chinook salmon f r y 46 Table 10. Number of male and female parents used i n experimental c r o s s e s of chinook salmon from stream- and ocean-type p o p u l a t i o n s 49 Table 11. Net movement scores f o r j u v e n i l e chinook salmon X i n n o c t u r n a l c u r r e n t response t e s t s 61 Table 12. Net movement scores f o r j u v e n i l e chinook salmon in d i u r n a l c u r r e n t response t e s t s 62 Table 13. Behaviour c o e f f i c i e n t s from p r i n c i p a l components a n a l y s i s of stream tank b e h a v i o u r a l i n t e r a c t i o n s among j u v e n i l e chinook salmon 64 Table 14. Covariance a n a l y s i s summary of s p e c i f i c growth r a t e data f o r stream- and ocean-type chinook salmon 71 Table 15. Body l e n g t h and freshwater s c a l e counts f o r a d u l t salmon and wet weights of newly-emerged f r y from Nanaimo River c r o s s e s 81 Table 16. Behaviour c o e f f i c i e n t s from p r i n c i p a l components a n a l y s i s of j u v e n i l e chinook salmon i n t e r a c t i o n 85 Table 17. Mean (+SE) aggression scores f o r j u v e n i l e chinook from the Nanaimo and Sq.uamish r i v e r s 88 Table 18. Percentage weight l o s s a f t e r 24 h i n 20%© seawater f o r j u v e n i l e chinook salmon 95 Table 19. Percentage s u r v i v a l a f t e r 24 h i n 30% o seawater fo r j u v e n i l e chinook salmon 97 Table 20. C o r r e l a t i o n s between p a r e n t a l freshwater l i f e h i s t o r y , from s c a l e c i r c u l u s counts, and progeny a g g r e s s i o n and s a l i n i t y t o l e r a n c e 99 Table 21. J u v e n i l e chinook l i f e h i s t o r y p a t t e r n s i n the Kamchatka River ( S o v i e t Union) and s e v e r a l New Zealand r i v e r s 147 Table 22. P r i n c i p a l components a n a l y s i s of environmental v a r i a b l e s c h a r a c t e r i s t i c of p o p u l a t i o n s of chinook s a l m o n 157 T a b l e 2 3 . P h y s i c a l m e a s u r e m e n t s r e c o r d e d a t f i s h m i c r o h a b i t a t s 183 T a b l e 24. P r i n c i p a l c o m p o n e n t s a n a l y s i s o f m i c r o h a b i t a t u s e by j u v e n i l e c h i n o o k a n d c o h o s a l m o n 186 T a b l e 2 5. M a t r i x o f M a h a l a n o b i s d i s t a n c e s among m i c r o h a b i t a t c e n t r o i d s f o r j u v e n i l e c h i n o o k a n d c o h o s a l m o n , 1985 191 T a b l e 26. M a t r i x o f M a h a l a n o b i s d i s t a n c e s among m i c r o h a b i t a t c e n t r o i d s f o r j u v e n i l e c h i n o o k a n d c o h o s a l m o n , 1986 195 T a b l e 27. A v e r a g e w a t e r v e l o c i t i e s a n d w a t e r d e p t h s i n s u b s e c t i o n s o f J o n e s C r e e k e x p e r i m e n t a l s t r e a m s e c t i o n s 204 T a b l e 28. Number (mean+SE) o f c h i n o o k f o u n d i n p o o l h a b i t a t s i n J o n e s C r e e k 221 T a b l e 29. Number (+SE) o f c h i n o o k f o u n d i n r i f f l e h a b i t a t s i n J o n e s C r e e k 222 LIST OF FIGURES F i g u r e 1. Geographic l o c a t i o n of v a r i o u s study p o p u l a t i o n s of chinook salmon 11 F i g u r e 2. Mean aggression scores f o r newly-emerged, w i l d -reared chinook salmon f r y in MIS t e s t s 29 F i g u r e 3. Mean agg r e s s i o n scores f o r newly-emerged, w i l d -reared chinook salmon f r y in stream tank t e s t s 33 F i g u r e 4. Mean agg r e s s i o n scores f o r newly-emerged, l a b o r a t o r y - r e a r e d chinook salmon f r y i n MIS t e s t s 36 F i g u r e 5. Mean stream tank aggression scores f o r l a b o r a t o r y - r e a r d e d chinook f r y 40 F i g u r e 6. Major f e a t u r e s of the Nanaimo R i v e r i n c l u d i n g spawning areas ( s t i p p l i n g ) of "Lower Nanaimo" (A) and "1st Lake" (B) p o p u l a t i o n s of chinook salmon i n the r i v e r 52 F i g u r e 7. Net movement scores f o r stream- and ocean-type j u v e n i l e chinook salmon i n c u r r e n t response t e s t s 58 F i g u r e 8. Mean (+SE) aggression scores f o r j u v e n i l e chinook salmon f o r Nanaimo R i v e r and S l i m Creek p o p u l a t i o n s at s e v e r a l ages 65 F i g u r e 9. S p e c i f i c growth r a t e f o r stream- and ocean-type chinook salmon from emergence to 12 months of age 69 F i g u r e 10. Photomicrograph of a d u l t chinook salmon s c a l e i l l u s t r a t i n g key f e a t u r e s used to determine j u v e n i l e l i f e h i s t o r y p a t t e r n 74 x i i i F i g u r e 11. R e l a t i o n s h i p b e t w e e n f e m a l e s t a n d a r d l e n g t h a n d f r y wet w e i g h t a t emergence f o r Nanaimo R i v e r c h i n o o k s a l m o n 82 F i g u r e 12. Mean (+SE) a g g r e s s i o n s c o r e s f o r j u v e n i l e c h i n o o k s a l m o n f r o m t h e Nanaimo R i v e r f a m i l i e s a n d S q u a m i s h R i v e r o v e r 3 months o f age 86 F i g u r e 13. R e l a t i o n s h i p b e t w e e n body s i z e a n d m e a s u r e s o f s a l i n i t y t o l e r a n c e i n j u v e n i l e c h i n o o k s a l m o n o v e r 3 months o f age 90 F i g u r e 14. C h a n g e s i n p e r c e n t a g e s u r v i v a l a f t e r e x p o s u r e t o 30%©seawater w i t h t i m e i n Nanaimo a n d S q u a m i s h r i v e r s c h i n o o k o v e r t h e i r f i r s t 3 months o f age 93 F i g u r e 15. T r i v a r i a t e p l o t o f t h e r e l a t i v e r a n k s o f mean p a r e n t a l f r e s h w a t e r c i r c u l i c o u n t a nd t h e r a n k s o f a g g r e s s i v e b e h a v i o u r a n d s a l i n i t y t o l e r a n c e o f t h e i r p r o g e n y 101 F i g u r e 16. G e o g r a p h i c d i s t r i b u t i o n o f c h i n o o k s a l m o n i n t h e N o r t h P a c i f i c Ocean 121 F i g u r e 17. D i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r i e s f o r c h i n o o k s a l m o n s p a w n i n g p o p u l a t i o n s i n t h e S a c r a m e n t o a n d K l a m a t h r i v e r s , C a l i f o r n i a 126 F i g u r e 18. D i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r y p a t t e r n s f o r c h i n o o k s a l m o n s p a w n i n g p o p u l a t i o n s i n O r e g o n c o a s t a l s t r e a m s 129 F i g u r e 19. D i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r y p a t t e r n s f o r c h i n o o k s a l m o n s p a w n i n g p o p u l a t i o n s o f t h e C o l u m b i a R i v e r 132 x i v F i g u r e 20. D i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r y p a t t e r n s f o r c h i n o o k s a l m o n s p a w n i n g p o p u l a t i o n s o f c o a s t a l W a s h i n g t o n a n d P u g e t Sound 137 F i g u r e 2 1 . D i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r y p a t t e r n s i n c h i n o o k s a l m o n s p a w n i n g p o p u l a t i o n s i n s o u t h e r n B r i t i s h C o l u m b i a 139 F i g u r e 22. D i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r y p a t t e r n s i n c h i n o o k s p a w n i n g p o p u l a t i o n s i n n o r t h e r n B.C. a n d A l a s k a 144 F i g u r e 23. R e l a t i o n s h i p b e t w e e n mean a n n u a l a i r t e m p e r a t u r e a n d mean a n n u a l w a t e r t e m p e r a t u r e f o r s t u d y s t r e a m s ....152 F i g u r e 24. P l o t o f p r i n c i p a l component s c o r e s o f s t r e a m -a n d o c e a n - t y p e p o p u l a t i o n s a l o n g component a x e s 1 a n d 2 158 F i g u r e 25. I n t e r s p e c i f i c a g g r e s s i o n i n d i c e s b e t w e e n c o h o a n d c h i n o o k s a l m o n f r y 178 F i g u r e 26. P l o t s o f mean (+SE) p r i n c i p a l component s c o r e s s u m m a r i z i n g m i c r o h a b i t a t u s e by j u v e n i l e c o h o a n d c h i n o o k s a l m o n , 1 985 188 F i g u r e 27. P l o t s o f mean (+SE) p r i n c i p a l component s c o r e s s u m m a r i z i n g m i c r o h a b i t a t u s e by j u v e n i l e c o h o a n d c h i n o o k s a l m o n , 1986 193 F i g u r e 28. The J o n e s C r e e k s p a w n i n g c h a n n e l f a c i l i t y 198 F i g u r e 29. R e l a t i o n s h i p b e t w e e n f i s h s i z e a n d w a t e r v e l o c i t y o f m i c r o h a b i t a t s o c c u p i e d 207 F i g u r e 30. T e m p o r a l c h a n g e s i n mean (+SE) p r o p o r t i o n o f t o t a l e m i g r a t i o n by j u v e n i l e s a l m o n i n t h e e x p e r i m e n t a l s t r e a m s e c t i o n s 211 F i g u r e 31. Mean (+SE) s i z e s of i n i t i a l and emigrant salmon j u v e n i l e s 214 Fi g u r e 32. Mean (+SE) p r o p o r t i o n emigration from experimental channel s e c t i o n s by chinook when in t r o d u c e d alone and with coho salmon 216 F i g u r e 33. R e l a t i v e use of pool and r i f f l e h a b i t a t s i n Jones Creek experimental stream s e c t i o n s by coho and chinook salmon 219 x v i ACKNOWLEDGEMENTS T h i s t h e s i s was c o m p l e t e d u n d e r t h e s u p e r v i s i o n o f D r . P.A. L a r k i n . I t h a n k h i m s i n c e r e l y f o r t h e g u i d a n c e , a d v i c e , a n d s u p p o r t t h a t he h a s p r o v i d e d so f r e e l y o v e r t h e l a s t f i v e y e a r s . More g e n e r a l l y , I w i l l a l w a y s a p p r e c i a t e , a n d be g r a t e f u l f o r , t h e c o n f i d e n c e t h a t he h a s d i s p l a y e d i n me s i n c e o u r f i r s t m e e t i n g . I a l s o am g r a t e f u l t o D r s . M.C. H e a l e y , D. S c h l u t e r , C C . L i n d s e y , a n d J.D. M c P h a i l f o r t h e i r e n t h u s i a t i c s u p p o r t w h i l e s e r v i n g on my r e s e a r c h c o m m i t t e e . A d d i t i o n a l t h a n k s a r e due D r s . H e a l e y , S c h l u t e r , L i n d s e y , a n d C F . Wehrhahn who r e a d , a n d p r o v i d e d c o n s t r u c t i v e c r i t i c i s m s o f , an e a r l i e r d r a f t o f t h i s t h e s i s . I h a v e b e n e f i t e d s u b s t a n t i a l l y f r o m t h e f r i e n d s h i p a n d a d v i c e f r o m numerous c o l l e a g u e s , most n o t a b l y C J . F o o t e , G. P o g s o n , S. C o u r t e n a y , a n d M. L a b e l l e , F o r a s s i s t a n c e i n t h e f i e l d and i n t h e l a b o r a t o r y I t h a n k W. G i b s o n , C J . F o o t e , A. T o m p k i n s , M. L a b e l l e , a n d R. G r e g o r y . I a l s o am i n d e b t e d t o Ms. H. Hahn who p r o v i d e d a d m i n i s t r a t i v e s u p p o r t a n d t o M e s s e r s A. B l a c h f o r d a n d J . M e s s e r o f t h e B i o l o g i c a l D a t a C e n t e r f o r a s s i s t a n c e w i t h c o m p u t i n g f a c i l i t i e s . R e s e a r c h f u n d i n g was p r o v i d e d by a N a t u r a l S c i e n c e s a n d E n g i n e e r i n g R e s e a r c h C o u n c i l o f Canada (NSERC) o p e r a t i n g g r a n t a w a r d e d t o P.A. L a r k i n . I a p p r e c i a t e p e r s o n a l s u p p o r t f r o m NSERC i n t h e f o r m o f r e s e a r c h a s s i s t a n t s h i p s , a n d g r a d u a t e f e l l o w s h i p s a w a r d e d by t h e U n i v e r s i t y o f B.C. The C a n a d i a n D e p a r t m e n t o f F i s h e r i e s a n d O c e a n s (DFO) i s a c k n o w l e d g e d f o r p r o v i d i n g a s s i s t a n c e d u r i n g c o l l e c t i o n o f a d u l t c h i n o o k s a l m o n . S p e c i f i c a l l y , I t h a n k P. P r e s t o n (Nanaimo R i v e r H a t c h e r y ) , D. H a r v e y a n d C. H a r r i s o n ( E a g l e R i v e r H a t c h e r y ) , L. K a h l ( C h e h a l i s R i v e r H a t c h e r y ) , D. C e l l i ( T e n d e r f o o t H a t c h e r y ) , B. Huber (DFO, P r i n c e G e o r g e ) , R. H a r r i s o n (DFO, F r a s e r R i v e r - Y u k o n ) , a n d t h e s t a f f s o f t h e L i t t l e Q u a l i c u m , a n d Q u e s n e l r i v e r s h a t c h e r i e s . The c o - o p e r a t i o n o f B.C. H y d r o a n d D. B u x t o n ( C h i l l i w a c k R i v e r H a t c h e r y ) i n p r o v i d i n g a c c e s s t o , and a c o m m o d a t i o n a t , t h e J o n e s C r e e k S p a w n i n g C h a n n e l F a c i l i t y i s g r a t e f u l l y a c k n o w l e d g e d . F o r p r o v i d i n g d a t a o r a c c e s s t o d a t a b a s e s o f a d u l t c h i n o o k s a l m o n s c a l e a g e s I t h a n k F. F i s h e r a n d T . J . M i l l s ( C a l i f . D e p t . o f F i s h a n d Game), J . W i l c o c k ( A l a s k a D e p t . o f F i s h a n d Game), M.J. Unwin (New Z e a l a n d D e p t . o f A g r i c u l t u r e a n d F i s h e r i e s ) , a n d C a m i l l e G o s l i n (DFO S c a l e M o r p h o l o g y L a b ) . I t h a n k my w i f e , N i n i , f o r h e r s u p p o r t , e n t h u s i a s m , a n d e n c o u r a g e m e n t . 1 GENERAL INTRODUCTION One o f t h e m a j o r g o a l s o f e v o l u t i o n a r y b i o l o g y i s t o p r o m o t e an u n d e r s t a n d i n g o f t h e c a u s e s a n d s i g n i f i c a n c e o f b i o l o g i c a l d i v e r s i t y . H i s t o r i c a l l y , e f f o r t s f o c u s s e d on e x p l a i n i n g t h e o r i g i n a n d p a t t e r n s o f v a r i a b i l i t y a t o r a b o v e t h e s p e c i e s l e v e l (Mayr 1963; Futuyma 1 9 8 8 ) . I n more r e c e n t t i m e s , t h e r e c o g n i t i o n o f e x t e n s i v e p h e n o t y p i c v a r i a b i l i t y among i n d i v i d u a l s w i t h i n p o p u l a t i o n s , a n d among p o p u l a t i o n s o f s i n g l e s p e c i e s h a s r e c e i v e d i n t e n s i v e s t u d y a n d p r o v i d e d t h e f o u n d a t i o n f o r modern e v o l u t i o n a r y t h e o r y o p e r a t i n g a t t h e p o p u l a t i o n l e v e l ( Mayr 1963; L e w o n t i n 1974; W r i g h t 1 9 7 8 ) . One a s p e c t o f s t u d i e s o f i n t r a - a n d i n t e r p o p u l a t i o n v a r i a b i l i t y t h a t i s c o n t r o v e r s i a l c o n c e r n s t h e d e b a t e o v e r t h e r e l a t i v e i m p o r t a n c e o f n a t u r a l s e l e c t i o n t o t h e m a i n t e n a n c e o f v a r i a b i l i t y i n m o r p h o l o g i c a l , b e h a v i o u r a l , p h y s i o l o g i c a l , a n d , most r e c e n t l y , b i o c h e m i c a l t r a i t s (Mayr 1963; N e i a n d Koehn 1983; E n d l e r 1986; Futuyma 1 9 8 6 ) . I f t h e f o r m o f s e l e c t i o n o f t r a i t s i m p o r t a n t t o s u r v i v a l o r m a t i n g s u c c e s s i n a p o p u l a t i o n i s " d i s r u p t i v e " , t h e n two o r more d i s t i n c t p h e n o t y p e s may be f a v o u r e d and s u c h p o p u l a t i o n s a r e r e f e r r e d t o a s p o l y m o r p h i c . F r e q u e n c y d e p e n d e n t s e l e c t i o n a n d e n v i r o n m e n t a l h e t e r o g e n e i t y a r e t h o u g h t t o be i m p o r t a n t i n m a i n t a i n i n g p o l y m o r p h i s m s ( M a t h e r 1955; Mayr 1963; E n d l e r 1 9 8 6 ) . A c r o s s t h e r a n g e o f a s p e c i e s , d i f f e r e n t s e l e c t i v e e n v i r o n m e n t s a s s o c i a t e d w i t h l o c a l p o p u l a t i o n s may r e s u l t i n a l t e r n a t i v e 2 p h e n o t y p e s b e i n g f a v o u r e d among p o p u l a t i o n s . T a x o n o m i c a l l y , s u c h s p e c i e s a r e p o l y t y p i c , w h i l e e c o l o g i c a l l y , t h e i r component p o p u l a t i o n s a r e e c o t y p e s o r e c o l o g i c a l r a c e s (Mayr 1 9 6 3 ) . The l i f e h i s t o r y o f an o r g a n i s m i s a p a t h w a y o r s e r i e s o f e v e n t s l e a d i n g t o s u c c e s s f u l r e p r o d u c t i o n . The s t u d y o f n a t u r a l s e l e c t i o n o f l i f e h i s t o r y t r a i t s o r p a t h w a y s may f o c u s on non-s e x u a l s e l e c t i o n d u r i n g n o n - r e p r o d u c t i v e l i f e h i s t o r y s t a g e s a n d / o r s e x u a l s e l e c t i o n d u r i n g t h e r e p r o d u c t i v e s t a g e . D i s c r e t e i n t r a - a n d i n t e r p o p u l a t i o n v a r i a b i l i t y i n r e p r o d u c t i v e l i f e h i s t o r y a r e e x e m p l i f i e d i n many p l a n t a n d a n i m a l g r o u p s ( v a n R h i j n 1973; Howard 1978; Anon 1984; C h i a r e l l o a n d R o u g h g a r d e n 1984; L o t t 1984; T a b o r s k y e t a l . 1 9 8 7 ) . I n a d d i t i o n t o a l t e r n a t i v e b r e e d i n g s y s t e m s a n d b e h a v i o u r s , d i s c r e t e v a r i a b i l i t y may be p r e s e n t i n l i f e h i s t o r y p a t t e r n s d u r i n g non-r e p r o d u c t i v e p e r i o d s . E x a m p l e s i n c l u d e s o c i a l o r g a n i z a t i o n i n v e r t e b r a t e s ( L o t t 1 9 8 4 ) , e x t e n t a n d m e c h a n i s m o f d i s p e r s a l a n d d u r a t i o n o f d i a p a u s e i n i n s e c t s ( H a r r i s o n 1980; T a u b e r a nd T a u b e r 1 9 8 1 ) , t r o p h i c m o r p h o l o g y a nd b e h a v i o u r , a n d h a b i t a t u se i n i n s e c t s a n d v e r t e b r a t e s ( K o r n f i e l d e t a l . 1982; C a r o a n d B a t e s o n 1986; S m i t h 1987; G a r d n e r e t a l . 1 9 8 8 ) . The S a l m o n i d a e a r e t e l e o s t f i s h e s t h a t e x h i b i t a l t e r n a t i v e l i f e h i s t o r y p a t t e r n s w i t h i n a n d b e t w e e n p o p u l a t i o n s , b o t h d u r i n g r e p r o d u c t i v e ( B e r g 1959; G r o s s 1985; M y e r s e t a l . 1986) and n o n - r e p r o d u c t i v e l i f e h i s t o r y s t a g e s ( C a m p b e l l 1977; H i n d a r a n d J o n s s o n 1982; Wood e t a l . 1987; M e t c a l f e e t a l . 1 9 8 8 ) . 3 E x t e n s i v e i n t e r p o p u l a t i o n v a r i a b i l i t y ( s e e R i c k e r 1972) i s p r o m o t e d by t h e d i v e r s e s e l e c t i v e e n v i r o n m e n t s o c c u p i e d by p o p u l a t i o n s o v e r e a c h s p e c i e s ' r a n g e a n d by t h e t e n d e n c y o f a d u l t s t o r e t u r n t o n a t a l a r e a s t o spawn a n d , h e n c e , t o be r e p r o d u c t i v e l y i s o l a t e d f r o m o t h e r p o p u l a t i o n s . The l i f e h i s t o r y o f anadromous s a l m o n i d s i n c l u d e s p e r i o d s o f f r e s h w a t e r s p a w n i n g by a d u l t s , i n c u b a t i o n o f e g g s a nd l a r v a e , a n d f r e s h w a t e r r e a r i n g by y o u n g f i s h , f o l l o w e d by m i g r a t i o n t o t h e s e a where i n d i v i d u a l s f e e d a n d grow t o m a t u r i t y b e f o r e r e t u r n i n g t o f r e s h w a t e r t o spawn. The d u r a t i o n o f f r e s h w a t e r r e a r i n g may v a r y among s p e c i e s f r o m l e s s t h a n 1 d a y t o s e v e r a l y e a r s (Hoar 1 9 7 6 ) . S i m i l a r l y , t h e d u r a t i o n o f t h e m a r i n e p h a s e i s h i g h l y v a r i a b l e ( a b o u t 1-6 y e a r s ) among s p e c i e s ( M i l l e r a n d B r a n n o n 1982; H e a l e y 1 9 8 6 ) . The c h i n o o k s a l m o n , O n c o r h y n c h u s t s h a w y t s c h a , i s an anadromous s p e c i e s n a t i v e t o t h e n o r t h P a c i f i c . O v e r i t s g e o g r a p h i c r a n g e , t h e c h i n o o k commonly e x h i b i t s two l i f e h i s t o r y p a t t e r n s d i s t i n g u i s h e d by t h e age a t w h i c h j u v e n i l e s m i g r a t e f r o m n a t a l s t r e a m s t o t h e s e a . G i l b e r t ( 1 9 1 3 ) f i r s t d e t a i l e d t h e s e a l t e r n a t i v e b e h a v i o u r a l t y p e s a n d r e f e r r e d t o t h o s e j u v e n i l e s t h a t m i g r a t e s e a w a r d a s u n d e r y e a r l i n g s , u s u a l l y d u r i n g t h e i r f i r s t t h r e e months o f l i f e , a s " s e a - " o r " o c e a n - t y p e " c h i n o o k a n d d e s i g n a t e d y e a r l i n g o r l a t e r m i g r a n t s a s " s t r e a m -t y p e " . T h e s e a l t e r n a t i v e l i f e h i s t o r i e s may be f o u n d w i t h i n a s i n g l e p o p u l a t i o n , b u t t h e y a l s o d i f f e r e n t i a t e p o p u l a t i o n s 4 d o m i n a t e d by one t y p e o r t h e o t h e r . S t r e a m - a n d o c e a n - t y p e m i g r a t o r y b e h a v i o u r s a p p e a r t o be g e n e t i c a l l y b a s e d ( R i c h a n d H o lmes 1928) a n d a r e a s s o c i a t e d w i t h g e n e t i c d i f f e r e n c e s i n m o r p h o l o g y and enzyme f r e q u e n c y ( C a r l and H e a l e y 1 9 8 4 ) . The j u v e n i l e l i f e h i s t o r y t y p e s a l s o show g e n e t i c d i f f e r e n c e s i n s e a s o n a l m i g r a t i o n t i m i n g a s a d u l t s ( R i c h and H olmes 1 9 2 8 ) . I n t h i s t h e s i s , I e x p l o r e t h e phenomenon o f s t r e a m - a n d o c e a n - t y p e l i f e h i s t o r i e s i n c h i n o o k and i t s v a r i a b i l i t y b o t h w i t h i n and among p o p u l a t i o n s . Two p r i n c i p a l q u e s t i o n s a r e a d d r e s s e d . F i r s t , do s t r e a m - a n d o c e a n - t y p e c h i n o o k d i f f e r g e n e t i c a l l y i n a s p e c t s o f j u v e n i l e p h e n o t y p e a p p r o p r i a t e f o r t h e i r d i f f e r e n t d u r a t i o n s o f f r e s h w a t e r r e s i d e n c e b e f o r e s m o l t i f i c a - t i o n ? S t a t e d a n o t h e r way, do s t r e a m - a n d o c e a n - t y p e l i f e h i s t o r i e s r e p r e s e n t a d a p t i v e d i v e r s i f i c a t i o n w i t h i n a s i n g l e s p e c i e s ? I n C h a p t e r 1, I a d d r e s s t h i s g e n e r a l q u e s t i o n by a s s e s s i n g p r e d i c t i o n s c o n c e r n i n g r e l a t i v e p e r f o r m a n c e o f s t r e a m - a n d o c e a n - t y p e j u v e n i l e s i n b e h a v i o u r a l , m o r p h o l o g i c a l , and p h y s i o l o g i c a l a t t r i b u t e s a s s o c i a t e d w i t h a l t e r n a t i v e r e a r i n g p a t t e r n s i n f i s h e s . B o t h w i l d - r e a r e d j u v e n i l e s a n d s a l m o n r e a r e d i n t h e l a b o r a t o r y a r e t e s t e d t o a s s e s s t h e d e g r e e o f g e n e t i c d i f f e r e n t i a t i o n b e t w e e n l i f e h i s t o r y t y p e s . The s e c o n d q u e s t i o n s a s k e d i s , what f a c t o r s i n t h e a b i o t i c a n d b i o t i c e n v i r o n m e n t o f j u v e n i l e s a l m o n may p r o m o t e d i f f e r e n t i a t i o n i n l i f e h i s t o r y ? C h a p t e r 2 p r e s e n t s a summary o f g e o g r a p h i c v a r i a b i l i t y i n j u v e n i l e l i f e h i s t o r y p a t t e r n a n d a d d r e s s e s a b i o t i c f a c t o r s w h i c h v a r y among t h e h a b i t a t s o f c h i n o o k 5 p o p u l a t i o n s and w h i c h m i g h t promote v a r i a t i o n i n j u v e n i l e l i f e h i s t o r y . C h a p t e r 3 a d d r e s s e s v a r i a b i l i t y among p o p u l a t i o n s i n t h e e x t e n t o f i n t e r a c t i o n w i t h o t h e r s p e c i e s as a b i o t i c f a c t o r w h i c h might i n f l u e n c e j u v e n i l e l i f e h i s t o r y . L a s t l y , I c o n s i d e r my f i n d i n g s i n l i g h t of t h e phenomenon o f f u n c t i o n a l d i v e r s i t y w i t h i n s p e c i e s , t h e g e n e t i c v e r s u s e n v i r o n m e n t a l c o n t r o l of t h e e x p r e s s i o n o f a l t e r n a t i v e l i f e h i s t o r i e s , and t h e p o s s i b l e s y m p a t r i c o r i g i n o f a l t e r n a t i v e l i f e h i s t o r y t y p e s i n s a l m o n . 6 CHAPTER 1: PHENOTYPIC CORRELATES OF L I F E HISTORY VARIATION IN JUVENILE CHINOOK SALMON I n t r o d u c t i o n S t e a r n s (1976) d e f i n e d a l i f e h i s t o r y " s t r a t e g y " as a s e t of co-adapted r e p r o d u c t i v e t r a i t s r e s u l t i n g from s e l e c t i o n i n a s p e c i f i c environment. W h i l e r e p r o d u c t i v e t r a i t s may p r o v i d e measures most c l o s e l y l i n k e d t o f i t n e s s , c h a r a c t e r i s t i c s of o t h e r s t a g e s of an organism's l i f e h i s t o r y t h a t i n f l u e n c e growth and/or s u r v i v a l can be i m p o r t a n t components of a l i f e h i s t o r y p a t t e r n . S e l e c t i o n d u r i n g p a r t i c u l a r l i f e h i s t o r y s t a g e s , o f t e n i n s p e c i f i c e n v i r o n m e n t s , may be d i f f e r e n t from s e l e c t i v e f a c t o r s o p e r a t i n g d u r i n g o t h e r l i f e h i s t o r y s t a g e s i n o t h e r e n v i r o n m e n t s . W i t h i n major t a x a , l i f e h i s t o r y p a t t e r n s v a r y w i d e l y and p h y s i o l o g i c a l , b e h a v i o u r a l , and m o r p h o l o g i c a l a s p e c t s of a phenotype a r e o f t e n i n t e r p r e t e d as a d a p t i v e c h a r a c t e r i s t i c s of a p a r t i c u l a r l i f e h i s t o r y stage ( e . g . g i l l s of amphibian l a r v a e , s t r u c t u r a l and b e h a v i o u r a l a d a p t a t i o n s t o p r e v e n t downstream d i s p l a c e m e n t i n b e n t h i c a q u a t i c i n v e r t e b r a t e s ) . The more s p e c t a c u l a r l i f e h i s t o r y v a r i a t i o n s may i n c o r p o r a t e a r a p i d t r a n s f o r m a t i o n or metamorphosis a s s o c i a t e d w i t h a d i s t i n c t h a b i t a t s h i f t (e.g. metamorphosis i n h o lometabolous i n s e c t s and a n u r a n s ) . C e r t a i n l y the t i m i n g of b o t h the metamorphosis and the accompanying h a b i t a t s h i f t a r e a s p e c t s of a l i f e h i s t o r y 7 t h a t may be s u b j e c t t o s e l e c t i o n (Werner 1 9 8 6 ) . W i l b u r ( 1 9 8 0 ) t e r m e d s u c h v a r i a t i o n i n l i f e c y c l e s " c o m p l e x l i f e - h i s t o r i e s " ; a t e r m most o f t e n a p p l i e d t o i n s e c t a n d a m p h i b i a n l i f e c y c l e s . A l e s s s t r i k i n g b u t s t i l l i m p r e s s i v e c o m p l e x l i f e h i s t o r y i s t h a t i n v o l v i n g a " p a r r - s m o l t t r a n s f o r m a t i o n " , o r s m o l t i f i c a t i o n , i n a n a dromous S a l m o n i d a e ( H o a r 1 9 8 8 ) . D u r i n g t h i s t r a n s f o r m a t i o n , s e v e r a l s p e c i e s o f j u v e n i l e s a l m o n a n d t r o u t c h a n g e f r o m s t r e a m - r e s i d e n t , t e r r i t o r i a l i n d i v i d u a l s t h a t l i v e i n a h y p o t o n i c e n v i r o n m e n t , a n d h a v e p a r r m a r k i n g s a n d b r i g h t l y c o l o u r e d f i n s , t o d o w n s t r e a m m i g r a t i n g , " s i l v e r y " a n d c o u n t e r s h a d e d , s c h o o l i n g a n i m a l s known a s " s m o l t s " t h a t s oon e n t e r p e l a g i c , h y p e r t o n i c n e a r - s h o r e m a r i n e h a b i t a t s . T h e r e f o r e , s m o l t i f i c a t i o n i n i t i a t e s a s e r i e s o f b e h a v i o u r a l , m o r p h o l o g i c a l , and p h y s i o l o g i c a l c h a n g e s a c c o m p a n i e d by a h a b i t a t s h i f t ( F o l m a r a n d D i c k h o f f 1980; M c C o r m i c k a n d S a u n d e r s 1987; H o a r 1 9 8 8 ) . As w i t h o t h e r a n i m a l m e t a m o r p h o s e s and h a b i t a t s h i f t s , t h e t i m i n g o f s m o l t i f i c a t i o n i s s u b j e c t t o c h a n g e by n a t u r a l s e l e c t i o n . S u c h c h a n g e s i n t h e t i m i n g o f d e v e l o p m e n t , o r h e t e r o c h r o n y ( G o u l d 1 9 7 7 ) , h a v e been i m p l i c a t e d i n t h e e v o l u t i o n a r y r a d i a t i o n w i t h i n t h e S a l m o n i d a e ( B a l o n 1980; M c C o r m i c k a n d S a u n d e r s 1 9 8 7 ) . I n d e e d , i n s a l m o n i d s t h e t i m i n g o f s m o l t i f i c a t i o n , a n d i t s a s s o c i a t e d p h e n o t y p i c c h a n g e s , v a r i e s w i d e l y b o t h b e t w e e n and w i t h i n s p e c i e s ( R a n d a l l e t a l . 1 9 8 7 ) . I n t h e P a c i f i c s a l m o n O n c o r h y n c h u s , p i n k s a l m o n ( 0 . g o r b u s c h a ) a p p e a r t o l a c k a s m o l t 8 t r a n s f o r m a t i o n and m i g r a t e s e a w a r d v e r y s o o n a f t e r t h e f r y emerge f r o m t h e i r g r a v e l n e s t s (< 1 g i n w e i g h t ) . They a r e s c h o o l i n g , n o n - t e r r i t o r i a l , " s i l v e r y " , a n d a r e a b l e t o o s m o r e g u l a t e i n , a n d d e v e l o p an e a r l y p r e f e r e n c e f o r , s e a w a t e r a s n e w l y - e m e r g e d f r y ( W e i s b a r t 1968; M c l n e r n e y 1964; H oar 1 9 8 8 ) . By c o n t r a s t , c o h o s a l m o n ( 0 . k i s u t c h ) a r e i n t o l e r a n t o f s e a w a t e r a s f r y , p r e f e r f r e s h o r low s a l i n i t y w a t e r , h a v e p a r r m a r k i n g s and b r i g h t l y c o l o u r e d f i n s , a n d a r e t e r r i t o r i a l a n d h i g h l y a g g r e s s i v e (Chapman 1962; M c l n e r n e y 1964; W e i s b a r t 1968; O t t o and M c l n e r n e y 1 9 7 0 ) . I n c o h o s a l m o n , s m o l t i f i c a t i o n most commonly o c c u r s a f t e r 1 o r 2 y e a r s i n f r e s h w a t e r a t 10 g o r more i n w e i g h t ( C l a r k e 1982; M c C o r m i c k a n d S a u n d e r s 1 9 8 7 ) . S i m i l a r p h e n o t y p i c c o n t r a s t s b e t w e e n c l o s e l y r e l a t e d s p e c i e s w i t h d i f f e r e n t j u v e n i l e l i f e h i s t o r i e s h a v e been d o c u m e n t e d i n S a l v e l i n u s ( F e r g u s o n a n d N o a k e s 1982, I 9 8 3 a , b ) a n d G a s t e r o s t e u s ( G a s t e r o s t e i d a e , B a k k e r a n d F e u t h - d e B r u i j n ( 1 9 8 8 ) ) . The c h i n o o k s a l m o n , 0. t s h a w y t s c h a , i s h i g h l y v a r i a b l e i n t h e d u r a t i o n o f f r e s h w a t e r r e s i d e n c e b e f o r e s m o l t i f i c a t i o n . I t i s t h e o n l y s p e c i e s o f P a c i f i c s a l m o n w i d e l y c h a r a c t e r i z e d by p o p u l a t i o n s o f i n d i v i d u a l s t h a t ( i ) s m o l t a n d m i g r a t e s e a w a r d a s u n d e r y e a r l i n g s ( i . e . o c e a n - t y p e ) , ( i i ) s m o l t a n d m i g r a t e s e a w a r d a s y e a r l i n g o r o l d e r j u v e n i l e s ( s t r e a m - t y p e ) , o r ( i i i ) c o n t a i n m i x t u r e s o f ( i ) a n d ( i i ) ( R a n d a l l e t a l . 1 9 8 7 ) . I n t h i s c h a p t e r I e x a m i n e v a r i a t i o n w i t h i n t h e c h i n o o k s a l m o n i n a s p e c t s o f j u v e n i l e p h e n o t y p e t h o u g h t t o be 9 a p p r o p r i a t e f o r d i f f e r e n t d u r a t i o n s of freshwater r e s i d e n c e . I s t u d i e d a g g r e s s i v e behaviour, response to water c u r r e n t ( r h e o t a x i s ) , growth r a t e , morphology, and s a l i n i t y t o l e r a n c e i n w i l d and l a b o r a t o r y reared j u v e n i l e chinook salmon from as many as e i g h t p o p u l a t i o n s with d i f f e r e n t freshwater l i f e h i s t o r i e s . The s p e c i f i c goals were t o : ( 1 ) assess the degree of d i f f e r e n t i a t i o n among p o p u l a t i o n s i n t r a i t s thought to be r e l a t e d to the d u r a t i o n of freshwater r e s i d e n c e before s m o l t i f i c a t i o n , ( 2 ) determine i f any observed phenotypic v a r i a b i l i t y has a g e n e t i c b a s i s , and ( 3 ) to a s s e s s , by examining v a r i a t i o n both between and w i t h i n p o p u l a t i o n s , the c l o s e n e s s of the l i n k a g e between aspects of j u v e n i l e phenotype and d u r a t i o n of freshwater r e s i d e n c e . The e s s e n t i a l h y p o t h e s i s of t h i s chapter was that stream-type chinook would be b e h a v i o u r a l l y , m o r p h o l o g i c a l l y , and p h y s i o l o g i c a l l y s p e c i a l i z e d f o r extended stream r e s i d e n c e while ocean-type chinook would be p h e n o t y p i c a l l y s p e c i a l i z e d f o r e a r l y seaward m i g r a t i o n . S p e c i f i c a l l y , stream-type salmon were expected to be more a g g r e s s i v e , show stronger p o s i t i v e r h e o t a x i s u n t i l age 1 year, be l e s s t o l e r a n t of s a l i n e water as f r y , and possess morphological t r a i t s thought to be important i n s o c i a l i n t e r a c t i o n d u r i n g t e r r i t o r a l stream r e s i d e n c e (e.g. deeper bodies, l a r g e r and more pigmented median f i n s ) compared to ocean-type chinook. 10 1. BEHAVIOURAL AND MORPHOLOGICAL VARIATION AMONG POPULATIONS OF NEWLY-EMERGED CHINOOK SALMON FRY „ M e t h o d s S t u d y p o p u l a t i o n s The f i r s t s e t o f e x p e r i m e n t s c o n c e r n e d w i l d a n d l a b o r a t o r y -r e a r e d c h i n o o k f r y f r o m f o u r p o p u l a t i o n s ( F i g . 1 ) : S l i m C r e e k , E a g l e R i v e r , H a r r i s o n R i v e r , a n d Nanaimo R i v e r . F r y c o l l e c t e d f r o m S l i m C r e e k a nd H a r r i s o n R i v e r were s t u d i e d i n 1985. B e c a u s e t h e s e w i l d f r y h a d e x p e r i e n c e d d i f f e r e n t i n c u b a t i o n a n d r e a r i n g e n v i r o n m e n t s t h a t m i g h t have i n f l u e n c e d s u b s e q u e n t j u v e n i l e b e h a v i o u r a nd m o r p h o l o g y , f r y f r o m • t h e s e two p o p u l a t i o n s a s w e l l a s f r o m t h e E a g l e a n d Nanaimo r i v e r s were r a i s e d f r o m e g g s i n t h e l a b o r a t o r y u n d e r i d e n t i c a l c o n d i t i o n s d u r i n g 1986. From s c a l e a n a l y s i s o f a d u l t s a n d f r o m f i e l d s u r v e y s , S l i m C r e e k a nd E a g l e R i v e r c h i n o o k a r e p r e d o m i n a t e l y (>95%) s t r e a m - t y p e a nd j u v e n i l e s o v e r w i n t e r i n f r e s h w a t e r ( S h e p h e r d e t a l . 1 9 8 6 a ) . By c o n t r a s t , c h i n o o k f r o m H a r r i s o n a n d Nanaimo r i v e r s a r e p r e d o m i n a t e l y o c e a n - t y p e ( S h e p h e r d e t a l . 1 9 8 6 a ) . The Nanaimo R i v e r e g g s came f r o m t h e " f a l l r u n " p o p u l a t i o n t h a t spawns i n t h e l o w e r Nanaimo R i v e r ; i t s f r y move d o w n s t r e a m t o t h e Nanaimo e s t u a r y s o o n a f t e r e m e r g i n g f r o m t h e i r g r a v e l n e s t s ( H e a l e y 1980; C a r l a n d H e a l e y 1 9 8 4 ) . I n f o r m a t i o n c o n c e r n i n g t h e s a l m o n i d p o p u l a t i o n s a n d F i g u r e 1. G e o g r a p h i c l o c a t i o n o f v a r i o u s s t u d y p o p u l a t i o n s o f c h i n o o k s a l m o n . ( 1) S l i m C r e e k , (2) Bowron R i v e r , (3) E a g l e R i v e r , (4) Salmon R i v e r , (5) H a r r i s o n R i v e r , (6) S q u a m i s h R i v e r , (7) Nanaimo R i v e r , ( 8 ) L i t t l e Q u a l i c u m R i v e r , ( 9 ) W a l k e r C r e e k , S t a r = V a n c o u v e r . 12 13 b i o p h y s i c a l f e a t u r e s o f t h e s t u d y r i v e r s c a n be f o u n d i n Brown an d M u s g r a v e ( 1 9 7 9 ) , H e a l e y ( 1 9 8 0 ) , M a r s h a l l a n d Manzon ( 1 9 8 0 ) , W h elan e t a l . ( 1 9 8 1 ) , H e a l e y and J o r d a n ( 1 9 8 2 ) , a n d S h e p h e r d e t a l . ( 1 9 8 6 a , b ) . C o l l e c t i o n a n d m a i n t e n a n c e o f w i l d f r y R e c e n t l y emerged c h i n o o k s a l m o n f r y were c o l l e c t e d f r o m H a r r i s o n R i v e r on A p r i l 10, 1985 u s i n g a b e a c h s e i n e a n d f r o m S l i m C r e e k u s i n g a 1.25 X 0.6 m f y k e n e t on t h e s p a w n i n g g r o u n d s on May 11-12. A l l f r y w e r e t r a n s p o r t e d t o t h e l a b o r a t o r y w i t h i n 12 h o f c a p t u r e . F r y were r e c o g n i z e d a s n e w l y - e m e r g e d by t h e i r s m a l l s i z e ( 32-36 mm s t a n d a r d l e n g t h ( S L ) ) , d e v e l o p m e n t a l s t a t e ( i . e . d e g r e e o f y o l k - s a c a b s o r p t i o n ) , a n d by m o n i t o r i n g t h e c o l l e c t i o n s i t e s f o r f i r s t a p p e a r a n c e o f f r y . I n t h e l a b o r a t o r y , f r y were m a i n t a i n e d i n 94 L a q u a r i a i n a c o n t r o l l e d o e n v i r o n m e n t chamber (10 C) on a 12 h l i g h t : 12 h d a r k p h o t o p e r i o d . F i s h were f e d a d i e t o f c r u s h e d T e t r a m i n f i s h f o o d t h r i c e d a i l y . Gamete c o l l e c t i o n a nd i n c u b a t i o n E g gs a n d m i l t were c o l l e c t e d f r o m r i p e , w i l d c h i n o o k s a l m o n d u r i n g S e p t e m b e r ( S l i m C r e e k a n d E a g l e R i v e r ) , O c t o b e r (Nanaimo R i v e r ) , a n d November ( H a r r i s o n R i v e r ) o f 1985. S l i m C r e e k a d u l t s were c o l l e c t e d on t h e s p a w n i n g g r o u n d s by e l e c t r o s h o c k i n g w h i l e a d u l t s f r o m t h e E a g l e , H a r r i s o n , a n d Nanaimo r i v e r s were 1 4 c o l l e c t e d a t f e n c e s o r by s e i n i n g i n c o n j u n c t i o n w i t h e nhancement o p e r a t i o n s . E g g s f r o m e a c h f e m a l e were k e p t s e p a r a t e a n d were f e r t i l i z e d w i t h t h e m i l t o f i n d i v i d u a l m a l e s i n t h e f i e l d ( S l i m C r . , 4 f e m a l e s X 7 m a l e s ; E a g l e R., 6 f e m a l e s X 4 m a l e s ; Nanaimo R., 3 f e m a l e s X 4 m a l e s ; H a r r i s o n R., 3 f e m a l e s X 2 m a l e s ) . F a c i l i t i e s f o r t r a n s p o r t a t i o n a n d s u b s e q u e n t i n c u b a t i o n a nd r e a r i n g o f s a l m o n were l i m i t e d , s o z y g o t e s were p o o l e d a f t e r f e r t i l i z a t i o n . Z y g o t e s were t r a n s p o r t e d (5 C) t o t h e l a b o r a t o r y a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a . E l a p s e d t i m e f r o m f e r t i l i z a t i o n t o p l a c e m e n t i n t h e i n c u b a t o r r a n g e d f r o m 2 h ( H a r r i s o n R i v e r ) t o 24 h ( S l i m C r e e k ) . The i n c u b a t i o n a p p a r a t u s c o n s i s t e d o f a l a r g e (1.8 m x 0.6 m x 0.9 m) c o o l i n g u n i t d e s c r i b e d by M u r r a y a n d M c P h a i l ( 1 9 8 8 ) . W i t h i n t h e c o o l i n g u n i t , z y g o t e s were i n c u b a t e d i n " c o r n e r t y p e " a q u a r i u m f i l t e r s w i t h a b o u t 3-4 cm o f pea g r a v e l . W a t e r f l o w t h r o u g h t h e i n c u b a t o r was s e t t o 2 L / m i n a n d t h e embryos a n d o l a r v a e were k e p t i n d a r k n e s s a t 5 C d u r i n g t h e a p p r o x i m a t e l y 7 months o f i n c u b a t i o n . Upon e m e r g e n c e , f r y were p l a c e d i n 94 L f i b e r g l a s s r e a r i n g t r o u g h s where t h e y were l e f t f o r 24 h. The w a t e r f l o w t h r o u g h t h e t r o u g h s was m a i n t a i n e d a t 4 L/min and f r y were f e d O r e g o n M o i s t P e l l e t (OMP) f o o d t h r i c e d a i l y on a s c h e d u l e o f i n c r e a s i n g p e l l e t s i z e s . The l i g h t s c h e d u l e f o l l o w e d t h e n a t u r a l p h o t o p e r i o d a n d was p r o v i d e d by a s i n g l e 40 W f l u o r e s c e n t b u l b p e r t r o u g h . A s i n g l e 25 W l i g h t b u l b c o n t r o l l e d by a r h e o s t a t -15 t i m e r s i m u l a t e d "dawn-dusk" e a c h d a y . A. R e s p o n s e o f n e w l y - e m e r g e d c h i n o o k f r y t o w a t e r c u r r e n t I n an a t t e m p t t o a s s e s s m i g r a t o r y " r e s t l e s s n e s s " i n n e w l y -emerged w i l d f r y (1985) a n d l a b o r a t o r y - r e a r e d f r y ( 1 9 8 6 ) , I s t u d i e d r h e o t a c t i c b e h a v i o u r d u r i n g c u r r e n t r e s p o n s e t e s t s . C u r r e n t r e s p o n s e t e s t s o f v a r i o u s d e s i g n s h a v e been e f f e c t i v e i n d e t e c t i n g d i f f e r e n c e s i n r h e o t a x i s among p o p u l a t i o n s t h a t c o r r e l a t e w e l l w i t h m i g r a t o r y b e h a v i o u r d i f f e r e n c e s o b s e r v e d i n n a t u r e ( e . g . R a l e i g h 1971; B r a n n o n 1972; K e l s o e t a l . 1981; L u n d q v i s t a n d E r i k s s o n 1985; T h o r p e e t a l . 1 9 8 8 ) . The. t e s t s were r u n i n two a r t i f i c i a l , o v a l - s h a p e d s t r e a m c h a n n e l s ( 3 . 8 m s t r e t c h e d l e n g t h ) . E a c h o f two c u r r e n t c h a n n e l s was s u b d i v i d e d i n t o 21 c o m p a r t m e n t s (0 . 1 5 X 0.20 X 0.25 m) r a n k e d f r o m -10 (most d o w n s t r e a m ) t h r o u g h 0 ( c e n t r a l c o m p a r t m e n t ) t o +10 (most u p s t r e a m ) . I n w i l d s a l m o n i d p o p u l a t i o n s most d o w n s t r e a m m i g r a t i o n i s n o c t u r n a l , b u t d i u r n a l d o w n s t r e a m movement i s o f t e n o b s e r v e d ( F o l m a r and D i c k h o f f 1980; G o d i n 1982; S h e p h e r d e t a l . 1 9 8 6 a ) . T h e r e f o r e , e a c h t r i a l a s s e s s e d t h e movements o f 20 c h i n o o k f r y t h r o u g h t h e c h a n n e l c o m p a r t m e n t s d u r i n g s u c c e s s i v e l i g h t ( " d i u r n a l " ) a n d d a r k ( " n o c t u r n a l " ) t e s t s . F r y w e r e p l a c e d i n t h e c e n t r a l c o m p a r t m e n t w i t h t h e e n t r a n c e a n d e x i t h o l e s b l o c k e d . A f t e r 0.5 h t h e l i g h t s were 16 e i t h e r dimmed ( n o c t u r a l t e s t s ) o r r a i s e d ( d i u r n a l t e s t s ) i n i n t e n s i t y o v e r a 0.5 h r p e r i o d . A f t e r 15 m i n , t h e s c r e e n s b l o c k i n g t h e h o l e s i n t h e c o m p a r t m e n t w a l l s were removed a n d t h e f i s h were f r e e t o move t h r o u g h t h e c o m p a r t m e n t h o l e s . A f t e r 2.25 h ( i . e . 2 h r a f t e r c o m p l e t e d a r k o r l i g h t c o n d i t i o n s were r e a c h e d ) , t h e d i s t r i b u t i o n o f f r y among t h e c o m p a r t m e n t s was r e c o r d e d . A f t e r a d i u r n a l o r n o c t u r n a l t e s t , f r y were r e t u r n e d t o t h e c e n t r a l c o m p a r t m e n t and l e f t f o r 0.5 h. A s e c o n d t e s t was t h e n r e p e a t e d u n d e r o p p o s i t e l i g h t c o n d i t i o n s ( i . e . i f t h e f i r s t t e s t was d i u r n a l , t h e s e c o n d was n o c t u r n a l o r v i c e v e r s a ) . F o r e a c h t e s t , a "movement s c o r e " was c a l c u l a t e d by summing t h e p r o d u c t s o f t h e number o f f i s h i n e a c h c o m p a r t m e n t a n d t h e r a n k o f t h a t c o m p a r t m e n t a n d t h e n d i v i d i n g by 20, t h e number o f f i s h i n e a c h t e s t . To p r o v i d e a n e t movement s c o r e t h e d o w n s t r e a m s c o r e was s u b t r a c t e d f r o m t h e u p s t r e a m s c o r e ; a c o n s t a n t o f 10 was a d d e d t o e l i m i n a t e n e g a t i v e s c o r e s . F o r e a c h p o p u l a t i o n t w e l v e t r i a l s , e a c h c o n s i s t i n g o f a n o c t u r n a l a n d a d i u r n a l t e s t , were r u n i n 1985 a n d t w e n t y i n 1986. F r y s i z e a v e r a g e d (SE) 32.6 ( 0 . 1 ) a n d 36.3 ( 0 . 1 ) mm SL r e s p e c t i v e l y f o r S l i m and H a r r i s o n f i s h i n 1985. D u r i n g t h e t e s t s on l a b o r a t o r y -r e a r e d f r y , s a l m o n a v e r a g e d (SE) 33.1 ( 0 . 3 ) , 31.6 ( 0 . 4 ) , 34.3 ( 0 . 3 ) , a n d 33.9 ( 0 . 2 ) mm SL f o r S l i m , E a g l e , N a naimo, a n d H a r r i s o n p o p u l a t i o n s r e s p e c t i v e l y . W a t e r t e m p e r a t u r e was m a i n t a i n e d b e t w e e n 10-10.5 C f o r a l l t e s t s a n d w a t e r v e l o c i t y t h r o u g h t h e c o m p a r t m e n t o p e n i n g s a v e r a g e d a b o u t 10 cm/s. A n a l y s i s o f v a r i a n c e , w i t h p o p u l a t i o n a s t h e m a i n e f f e c t , 17 f o l l o w e d by T u k e y ' s a p o s t e r i o r i means t e s t ( Z a r 1984) were u s e d t o t e s t s t a t i s t i c a l h y p o t h e s e s . B. A g g r e s s i v e b e h a v i o u r o f n e w l y - e m e r g e d c h i n o o k f r y A g g r e s s i v e b e h a v i o u r o f c h i n o o k was o b s e r v e d i n t e s t s b o t h w i t h i n d i v i d u a l f r y a n d g r o u p s o f f r y . I n t h e s i n g l e f r y t e s t s , 25 f r y f r o m e a c h p o p u l a t i o n were i s o l a t e d i n i n d i v i d u a l 9 L o a q u a r i a i n t h e c o n t r o l l e d e n v i r o n m e n t chamber (10 C ) . F r y were l e f t t o a c c l i m a t e i n t h e a q u a r i a f o r 1 wk. D u r i n g t h i s t i m e t h e y were f e d c r u s h e d T e t r a m i n t h r i c e d a i l y . E a c h a q u a r i u m was c o v e r e d on t h r e e s i d e s by b l a c k p l a s t i c t o p r e v e n t f r y i n a d j a c e n t a q u a r i a f r o m o b s e r v i n g one a n o t h e r . The a q u a r i a were p l a c e d on r a c k s t h e f r o n t s o f w h i c h were d r a p e d w i t h p l a s t i c s h e e t i n g w i t h o b s e r v a t i o n h o l e s . To p r o v i d e a e r a t i o n , e a c h a q u a r i u m h a d a s u b g r a v e l f i l t e r . F r y were o b s e r v e d d a i l y f o r s i g n s o f f e e d i n g w h i c h u s u a l l y commenced w i t h i n 2-4 d a f t e r t h e y were i s o l a t e d i n t h e a q u a r i a . F o r t h e t e s t s on w i l d f r y , p h o t o p e r i o d was m a i n t a i n e d a t 12 h l i g h t : 1 2 h d a r k w h i l e t h e t e s t s on l a b o r a t o r y - r e a r e d f r y were c o n d u c t e d u n d e r a n a t u r a l p h o t o p e r i o d r e g i m e . M i r r o r - i m a g e - s t i m u l a t i o n ( M I S , G a l l u p 1968) t e s t s were c o n d u c t e d a f t e r f r y h a d been i n t h e i r a q u a r i a f o r 7 d. R o s e n a u and M c P h a i l ( 1 9 8 7) u s e d t h e MIS t e c h n i q u e t o s t u d y n e w l y - e m e r g e d c o h o s a l m o n f r y and f o u n d t h a t f r y a g g r e s s i o n i n c r e a s e d f o r up t o 7 d a f t e r w h i c h a g g r e s s i o n s t a b i l i z e d . 18 To m i n i m i z e t h e i n f l u e n c e o f d a i l y v o l a t i l i t y o f b e h a v i o u r o f i n d i v i d u a l s , I u s e d r e p e a t e d m e a s u r e m e n t s when t e s t i n g j u v e n i l e s a l m o n ( M a r t i n a n d K r a e m e r 1 9 8 7 ) . T h i s i s e s p e c i a l l y a p p r o p r i a t e f o r t e s t i n g n e w l y - e m e r g e d s a l m o n b e c a u s e t h e i r b e h a v i o u r i s u n s t a b l e a s t h e y r e f i n e b e h a v i o u r s w i t h e x p e r i e n c e ( e . g . C o l e a n d N o a k e s 1980; M a r t i n a n d B a t e s o n 1 9 8 6 ) . D u r i n g t h e MIS t e s t s , a m i r r o r was p l a c e d i n an a q u a r i u m ( s e l e c t e d i n random o r d e r ) a n d a f t e r a 1 min p e r i o d , t h e b e h a v i o u r a l r e s p o n s e s o f t h e f r y ( T a b l e 1) were r e c o r d e d f o r 3 min u s i n g an OS-3 O b s e r v a t i o n a l S y s t e m s I n c . e v e n t r e c o r d e r . F r y s i z e a v e r a g e d (SE) 32.8 ( 0 . 1 ) a n d 34.7 ( 0 . 2 ) SL mm r e s p e c t i v e l y f o r S l i m a n d H a r r i s o n w i l d f i s h , a n d 31.9 ( 0 . 2 ) , 30.3 ( 0 . 3 ) , 34.9 ( 0 . 4 ) , a n d 34.1 ( 0 . 3 ) mm SL f o r S l i m , E a g l e , N a n aimo, a n d H a r r i s o n l a b o r a t o r y - r e a r e d s a l m o n r e s p e c t i v e l y . F i s h f e d v i g o r o u s l y a n d g a i n e d an a v e r a g e o f a l m o s t 10% o f t h e i r o r i g i n a l body w e i g h t o v e r t h e 7 d t e s t s . I n g r o u p f r y t e s t s , b e h a v i o u r a l r e a c t i o n s ( T a b l e 1) were o b s e r v e d among s i x t e e n n e w l y emerged c h i n o o k by s c a n s a m p l i n g i n r e p l i c a t e s t r e a m t a n k s e c t i o n s . The P l e x i g l a s s t r e a m c h a n n e l s e c t i o n s m e a s u r e d 1.0 X 0.30 X 0.25 m a n d w a t e r l e v e l was m a i n t a i n e d a t 0.22 m by an o v e r f l o w p i p e . The b o t t o m o f e a c h c h a n n e l s e c t i o n was c o v e r e d w i t h s a n d a n d g r a v e l (<1.0 cm d i a m e t e r ) t o a d e p t h o f 4.0 cm. I n f l o w i n g d e c h l o r i n a t e d w a t e r o ( 2 . 5 L/min) m a i n t a i n e d w a t e r t e m p e r a t u r e a t b e t w e e n 10 a n d 11 C. 19 Table 1. A g g r e s s i v e behaviours recorded f o r chinook salmon i n the study. (*MIS only, **stream tank t e s t s only, ***both MIS and stream tanks t e s t s ) . Behaviour D e f i n i t i o n Swim-against-mirror' Any swimming motion by a f i s h with i t s snout up touching the m i r r o r . (Rosenau and McPhail 1987) Approach' Nip' Charge' Any movement by one f i s h towards another (or i t s m i r r o r image) by swimming or d r i f t i n g ; t h i s behaviour u s u a l l y i n i t i a t e s c o n t e s t s and i s of t e n f o l l owed by a nip or l a t e r a l d i s p l a y (Kratt and Smith 1979) . Any b i t i n g motion made by one f i s h towards another; contact does not n e c e s s a r i l y occur and thus i n c l u d e s the " t h r e a t n i p " of Chapman (1962) . Any r a p i d , d i r e c t movement by an ag-gr e s s o r towards another f i s h ; t h i s behaviour i s d i s t i n g u i s h e d from ap-proach by r a p i d a c c e l e r a t i o n ( K r a t t and Smith 1979). Chase : L a t e r a l d i s p l a y * * * Wigwag' Any prolonged approach by one f i s h towards another followed by f l e -e i n g of the chased f i s h from the p o i n t where i t was o r i g i n a l l y s t a t i o n e d . E r e c t i o n of the d o r s a l and anal f i n s while motionless, o f t e n ac-companied by e r e c t i o n of the p e l v i c and p e c t o r a l f i n s , lowering of the lower jaw, and " q u i v e r i n g " of the body; corresponds to the " l a t e r a l t h r e a t " of Chapman (1962) and Hartman (1965). L a t e r a l d i s p l a y s while swimming i n an exaggerated motion with the mouth open and lowering of the p e c t o r a l and p e l v i c f i n s ; may be performed while body i s h o r i z o n t a l , or i n c l i n e d upwards (head- up wigwag) or downwards (head-down wigwag ). (North 1979) 20 P h o t o p e r i o d was m a i n t a i n e d a t 12 h l i g h t : 1 2 h d a r k ( w i l d f r y t e s t s ) o r f o l l o w e d t h e n a t u r a l l i g h t : d a r k s c h e d u l e ( l a b o r a t o r y -r e a r e d f r y t e s t s ) . S i z e s o f n e w l y - e m e r g e d f r y were s l i g h t l y l a r g e r t h a n t h o s e r e p o r t e d f o r MIS t e s t s , a b o u t 33-36 mm S L . I n e a c h t e s t , 16 f r y f r o m t h e p o p u l a t i o n b e i n g t e s t e d were p l a c e d i n t h e s t r e a m t a n k s e c t i o n s a n d l e f t f o r 48 h d u r i n g w h i c h t i m e t h e y were f e d t h r i c e d a i l y w i t h c r u s h e d T e t r a m i n . F o r 5 c o n s e c u t i v e d a y s t h e r e a f t e r , t h e number a n d d u r a t i o n o f a g g r e s s i v e b e h a v i o u r s among f r y o v e r 10 m i n were r e c o r d e d t h r i c e d a i l y f o r e a c h s t r e a m t a n k s e c t i o n . F i s h were f e d a f t e r e a c h o b s e r v a t i o n p e r i o d and a t l e a s t 2 h e l a p s e d b e t w e e n o b s e r v a t i o n p e r i o d s . D a t a on t h e d u r a t i o n o f a g g r e s s i v e b e h a v i o u r s were s u m m a r i z e d by p r i n c i p a l c o m p o n e n t s a n a l y s i s (PCA) u s i n g MIDAS (F o x a n d G u i r e 1 9 7 6 ) . P r i n c i p a l c o m p o n e n t s a n a l y s i s p r o d u c e d s u m m a r i e s o f a g g r e s s i v e b e h a v i o u r c o n s i s t i n g o f one o r more i n d e p e n d e n t b e h a v i o u r a l v e c t o r s a s an e f f i c i e n t a l t e r n a t i v e t o e x a m i n i n g b e h a v i o u r a l v a r i a t i o n c h a r a c t e r - b y - c h a r a c t e r ( c f . H u n t i n g f o r d 1976; N i s h i k a w a 1 9 8 5 ) . F o r e a c h o b s e r v a t i o n p e r i o d , p r i n c i p a l component s c o r e s a l o n g t h o s e component a x e s t h a t a c c o u n t e d f o r 5% o r more o f t h e t o t a l v a r i a n c e were c a l c u l a t e d a n d s u b j e c t e d t o r e p e a t e d m e a s u r e s a n a l y s i s o f v a r i a n c e w i t h p o p u l a t i o n a s t h e m a i n e f f e c t . A p o s t e r i o r i means t e s t s were c o n d u c t e d u s i n g T u k e y ' s t e s t . 21 C. C h i n o o k f r y m o r p h o l o g y D u r i n g f r e s h w a t e r s t r e a m r e s i d e n c e , j u v e n i l e s a l m o n i d s h a v e d e e p b o d i e s w i t h p a r r m a r k s , and l a r g e , o f t e n f a l c a t e a n d b r i g h t l y c o l o u r e d f i n s . T h e s e body f o r m a nd c o l o u r a t i o n t r a i t s a r e t h o u g h t t o f u n c t i o n , i n p a r t , i n s o c i a l i n t e r a c t i o n ( H a r t m a n 1965; Maeda a n d H i d a k a 1979; K e e n l e y s i d e 1 9 7 9 ) . As p a r t o f t h e s m o l t t r a n s f o r m a t i o n , j u v e n i l e s become more s t r e a m l i n e d , t h e y l o s e t h e i r p a r r m a r k i n g s a n d become " s i l v e r y " a n d c o u n t e r s h a d e d . A l s o , c o l o u r a t i o n i n t h e f i n s f a d e s a n d t h e f i n s become s m a l l e r i n r e l a t i o n t o body s i z e ( F e s s l e r a n d Wagner 1969; Hoar 1976, 1988; W i n a n s a n d N i s h i o k a 1984; T a y l o r unpub. d a t a ) . T h e s e m o r p h o l o g i c a l t r a i t s a r e n o t o n l y f e a t u r e s o f t h e l i f e h i s t o r y t r a n s i t i o n w i t h i n an i n d i v i d u a l , b u t a l s o c h a r a c t e r i z e s p e c i e s a n d p o p u l a t i o n s w i t h i n s p e c i e s w i t h v a r i a b l e m i g r a t i o n t i m i n g ( H i k i t a 1962; Hoar 1976; C a r l a n d H e a l e y 1 9 8 4 ) . S t r e a m - t y p e c h i n o o k s h o u l d t h u s p o s s e s s d e e p e r b o d i e s , more p a r r m a r k s , a n d l a r g e r a n d more b r i g h t l y c o l o u r e d m e d i a n f i n s t h a n e a r l i e r m i g r a t i n g o c e a n - t y p e c h i n o o k s a l m o n . M o r p h o l o g i c a l a n a l y s i s on p r e s e r v e d ( 1 0 % b u f f e r e d f o r m a l i n ) n e w l y - e m e r g e d c h i n o o k f r y s c o r e d t h e f o l l o w i n g body m e a s u r e m e n t s : s t a n d a r d l e n g t h , maximum body d e p t h , h e a d d e p t h , h e a d l e n g t h , d o r s a l a n d a n a l f i n h e i g h t s , d o r s a l a n d a n a l f i n l e n g t h s , a n d c a u d a l f i n d e p t h (Hubbs and L a g l e r 1 9 6 7 ) . I a l s o c o u n t e d t h e number o f m a j o r p a r r m a r k s ( i . e . t h o s e b i s e c t i n g t h e l a t e r a l l i n e ) , a n d t o t a l p a r r m a r k s a n d t o o k m e a s u r e m e n t s o f 22 maximum p a r r mark l e n g t h and w i d t h . A l l m e a s u r e s e x c e p t s t a n d a r d l e n g t h and c o u n t s were made on t h e l e f t s i d e u n d e r a d i s s e c t i n g m i c r o s c o p e f i t t e d w i t h a m i c r o m e t e r e y e p i e c e . S t a n d a r d l e n g t h was m e a s u r e d w i t h V e r n i e r c a l i p e r s . A g e n e r a l e v a l u a t i o n o f c o l o u r a t i o n o f t h e body and f i n s o f f r y was made on a n a e s t h e t i s e d s p e c i m e n s a f t e r t h e s t r e a m t a n k t e s t s . To m i n i m i z e s i z e - r e l a t e d d i f f e r e n c e s i n body s h a p e , body m e a s u r e m e n t s were a d j u s t e d t o t h e o v e r a l l s a m p l e mean s t a n d a r d l e n g t h by c o v a r i a n c e a n a l y s i s on l o g l o t r a n s f o r m e d d a t a . To a s s e s s d i f f e r e n c e s i n a d j u s t e d means among p o p u l a t i o n s , p a i r w i s e , t - t e s t s were u s e d and </. was s e t 0.05/k, were k i s t h e number o f p a i r w i s e t e s t s . R e s u l t s A. R e s p o n s e o f n e w l y - e m e r g e d f r y t o w a t e r c u r r e n t W i l d f r y D u r i n g d i u r n a l t e s t s , n e w l y - e m e r g e d w i l d o c e a n - a n d s t r e a m -t y p e f r y r e s p o n d e d w i t h s l i g h t b u t s i g n i f i c a n t ( t - t e s t s f o r P=10, H a r r i s o n P < 0.01; S l i m P < 0.05, d f = 1 l ) u p s t r e a m movement ( T a b l e 2 ) . The mean number o f f r y m a k i n g an u p s t r e a m c h o i c e t e n d e d t o be h i g h e r f o r s t r e a m - t y p e , S l i m C r e e k f i s h t h a n f o r H a r r i s o n R i v e r o c e a n - t y p e f i s h ( e i g h t and s i x f r y r e s p e c t i v e l y ) . The d o w n s t r e a m r e s p o n s e o f f r y f r o m b o t h p o p u l a t i o n s u n d e r n o c t u r n a l t e s t c o n d i t i o n s was p r o n o u n c e d ( b o t h P < 0.0001, 23 T a b l e 2. N e t movement s c o r e s f o r n e w l y - e m e r g e d w i l d c h i n o o k s a l m o n f r y . V a l u e s a r e means, +SE ( r a n g e ) . N e t movement s c o r e 0=maximum d o w n s t r e a m movement, 1fJ=no n e t movement u p s t r e a m o r d o w n s t r e a m a n d 20=maximum u p s t r e a m movement. F o r t e s t s o f e q u a l i t y o f means ***P<0.001. N=12 f o r e a c h p o p u l a t i o n . S l i m H a r r i s o n C r e e k R i v e r ( S t r e a m - t y p e ) ( O c e a n - t y p e ) D i u r n a l t e s t s 10.9+0.57 10.9+0.35 ( 8 . 5 - 1 4 . 1 ) ( 8 . 7 - 1 3 . 1 ) N o c t u r n a l t e s t s * * * 4.1+0.63 0.4+0.17 (1 .2-7.1 ) ( 0 . 0 - 1 . 6 ) 24 d f = 1 l ) . H a r r i s o n R i v e r , o c e a n - t y p e c h i n o o k f r y , h o w e v e r , showed more p r o n o u n c e d d o w n s t r e a m movement t h a n s t r e a m - t y p e f r y f r o m S l i m C r e e k ( T a b l e 2, P < 0.0001, d f = 1 , 2 2 ) . D u r i n g t h e n o c t u r n a l t e s t s , an a v e r a g e o f 92% o f H a r r i s o n R i v e r c h i n o o k f r y moved t o t h e most d o w n s t r e a m c o m p a r t m e n t . By c o n t r a s t , w h i l e S l i m C r e e k c h i n o o k a l s o moved d o w n s t r e a m , an a v e r a g e o f o n l y 40% moved t o t h e most d o w n s t r e a m c o m p a r t m e n t a n d , h e n c e , t h e y t e n d e d t o be more e v e n l y d i s t r i b u t e d among t h e c o m p a r t m e n t s . Whereas i n t h r e e n o c t u r n a l t e s t s a t l e a s t 1 S l i m C r e e k f r y moved u p s t r e a m , no H a r r i s o n R i v e r c h i n o o k moved u p s t r e a m . L a b o r a t o r y - r e a r e d f r y I n t h e s t r e a m c h a n n e l s , t h e l a b o r a t o r y - r e a r e d c h i n o o k f r y f r o m a l l p o p u l a t i o n s r e s p o n d e d by " h o l d i n g " o r swimming s l i g h t l y u p s t r e a m d u r i n g d i u r n a l t e s t s w h i l e m o v i n g d o w n s t r e a m d u r i n g n o c t u r n a l t e s t s ( T a b l e 3 ) . I n o r d e r o f i n c r e a s i n g d o w n s t r e a m movement d u r i n g n o c t u r n a l t e s t s t h e p o p u l a t i o n s r a n k e d N anaimo, S l i m , E a g l e , a n d H a r r i s o n . I n o r d e r o f i n c r e a s i n g u p s t r e a m movement d u r i n g d i u r n a l t e s t s , t h e p o p u l a t i o n s r a n k e d : H a r r i s o n , E a g l e , S l i m , a n d N a n aimo. F r y movement t e n d e d t o be more p r o n o u n c e d d u r i n g n o c t u r n a l t e s t s . A l l p o p u l a t i o n s showed s i g n i f i c a n t d o w n s t r e a m movement ( t ^ - t e s t s f o r p = l 0 , a l l P < 0.001, d f = l 9 ) , b u t d u r i n g d i u r n a l t e s t s a l l p o p u l a t i o n s , e x c e p t H a r r i s o n R i v e r , showed s l i g h t , b u t s i g n i f i c a n t , u p s t r e a m movement (P < 0.05, T a b l e 3 ) . O c e a n - t y p e f r y f r o m t h e H a r r i s o n R i v e r h a d a s i g n i f i c a n t l y l o w e r n e t movement s c o r e (P < 0.0001, 25 T a b l e 3. N e t movement s c o r e s f o r n e w l y - e m e r g e d , l a b o r a t o r y -r e a r e d c h i n o o k s a l m o n f r y . V a l u e s a r e mean (SE) a n d i n a l l c a s e s N=20. U n d e r l i n i n g i n d i c a t e s t h o s e mean s c o r e s w h i c h a r e n o t s i g n i f i c a n t l y d i f f e r e n t by T u k e y ' s t e s t (P > 0 . 0 5 ) . A s c o r e o f 0=maximum d o w n s t r e a m movement, 10=no n e t movement u p s t r e a m o r down S t r e a m - t y p e O c e a n - t y p e S l i m C r e e k E a g l e R i v e r N anaimo R i v e r H a r r i s o n R i v e r D i u r n a l t e s t s 1 1 .74 ( 0 . 4 3 ) 10.90 ( 0 . 4 7 ) 12.28 ( 0 . 4 1 ) 1 0.44 ( 0 . 4 4 ) N o c t u r n a l t e s t s 6.37 ( 0 . 4 4 ) 6.14 ( 0 . 4 4 ) 7.48 ( 0 . 4 2 ) 3.02 ( 0 . 4 3 ) O v e r a l l 8.99 8.51 9.98 6.64 ( 0 . 3 1 ) ( 0 . 3 5 ) ( 0 . 3 8 ) ( 0 . 3 1 ) 26 d f = 3 , 7 6 ) d u r i n g n o c t u r n a l t e s t s t h a n f r y f r o m t h e t h r e e o t h e r p o p u l a t i o n s . B. A g g r e s s i v e b e h a v i o u r o f n e w l y - e m e r g e d c h i n o o k s a l m o n f r y W i l d f r y I n MIS t e s t s , most f r y a d j u s t e d q u i c k l y t o t h e p r e s e n c e o f t h e m i r r o r . F r y t y p i c a l l y o r i e n t e d t o w a r d s t h e i r m i r r o r i m a g e , t h e n g r a d u a l l y a p p r o a c h e d t h e m i r r o r and f o l l o w e d w i t h b o u t s o f " s w i m - a g a i n s t - m i r r o r " a n d " l a t e r a l d i s p l a y " . B o t h t h e t i m e i t t o o k f r y t o show some o v e r t r e a c t i o n t o t h e i r m i r r o r image a n d t o a p p r o a c h i t d e c r e a s e d o v e r t h e 7 d t e s t s . F r y were o c c a s i o n a l l y o b s e r v e d t o " c h a r g e " and e v e n " n i p " t h e i r m i r r o r i m a g e s b u t t h e s e b e h a v i o u r s were o b s e r v e d s o i n f r e q u e n t l y t h a t t h e y were n o t i n c l u d e d i n t h e a n a l y s i s . P r i n c i p a l c o m p o n e n t s a n a l y s i s o f t h e d a t a f r o m t h e MIS t e s t s s u m m a r i z e d 94% o f t h e b e h a v i o u r a l v a r i a t i o n i n two component a x e s ( T a b l e 4 ) . As i n d i c a t e d by t h e i r l a r g e component c o e f f i c i e n t s " s w i m - a g a i n s t - m i r r o r " d o m i n a t e d t h e f i r s t a x i s w h i l e "wigwag" d o m i n a t e d t h e s e c o n d a x i s . O v e r a l l d a y s c o m b i n e d , S l i m C r e e k , s t r e a m - t y p e c h i n o o k f r y were more a g g r e s s i v e t h a n o c e a n - t y p e f r y f r o m t h e H a r r i s o n R i v e r ( F i g . 2 a , P = 0.001, d f = 1 , 4 8 ) . A l o n g t h i s f i r s t c o m p o n e n t , f r y f r o m t h e two p o p u l a t i o n s showed d i f f e r e n t b e h a v i o u r a l t r e n d s w i t h t i m e . S l i m C r e e k f r y were h i g h l y r e s p o n s i v e t o t h e i r m i r r o r Table 4. P r i n c i p a l component c o e f f i c i e n t s d e r i v e d from MIS b e h a v i o u r a l data. C o e f f i c i e n t from PCA Behaviour Component 1 Component 2 Approach -0 .023 0. .005 Swim-against-mi r r o r -0 .996 0. .001 L a t e r a l d i s p l a y 0 .009 -0. .469 Wigwag -0 .006 -o, .883 Cumulative % t o t a l v a r i a n c e 81.3 93.5 6 28 i m a g e s f r o m o b s e r v a t i o n day 1, b u t d e c l i n e d somewhat i n "swim-a g a i n s t - m i r r o r " b e h a v i o u r t h r o u g h t o o b s e r v a t i o n d a y 7. By c o n t r a s t , H a r r i s o n R i v e r f r y showed l i t t l e r e s p o n s e a t t h e s t a r t o f t e s t i n g b u t s t e a d i l y i n c r e a s e d up t o o b s e r v a t i o n day 6 (day X p o p u l a t i o n P = 0.002, d f = 6 , 2 3 4 ) . A l o n g t h e s e c o n d component a x i s ("wigwag") S l i m C r e e k , s t r e a m - t y p e f r y were a l s o more a g g r e s s i v e t h a n t h e H a r r i s o n R i v e r n e w l y - e m e r g e d f r y ( F i g . 2b, P = 0 . 0 0 6 ) . F r y s p e n t more t i m e p e r f o r m i n g a g g r e s s s i v e d i s p l a y s a s t i m e p r o g r e s s e d ( F i g 2b) . I n t h e s t r e a m t a n k s , t h e j u v e n i l e c h i n o o k s a l m o n d e f e n d e d e x c l u s i v e a r e a s a n d a c t i v e l y d r o v e away i n t r u d e r s by o v e r t a g g r e s s i o n ( " n i p p i n g " and " c h a r g i n g " ) o r by a d v e r t i s e m e n t ( " l a t e r a l d i s p l a y s " a nd " wigwags") a n d a p p e a r e d t o f o r m t e r r i t o r i a l " m o s a i c s " ( K e e n l e y s i d e 1 9 7 9 ) . I n d i v i d u a l s t e n d e d t o r e m a i n i n s p e c i f i c a r e a s w h i l e m a k i n g b r i e f a g g r e s s i v e a n d f e e d i n g f o r a y s t o o t h e r l o c a t i o n s i n t h e s t r e a m t a n k s . C e r t a i n f i s h (1-4 p e r s e c t i o n ) u s u a l l y a c c o u n t e d f o r most o f t h e i n t e r a c t i o n . T h e s e " d o m i n a n t " f i s h u s u a l l y m a i n t a i n e d a t e r r i t o r y a t t h e most u p s t r e a m end o f t h e s t r e a m t a n k s e c t i o n s . Two component a x e s were p r o d u c e d by PCA w h i c h s u m m a r i z e d 8 9 % o f t h e t o t a l b e h a v i o u r a l v a r i a t i o n ; " l a t e r a l d i s p l a y " a n d "wigwag" b e h a v i o u r s d o m i n a t e d t h e f i r s t a n d s e c o n d component a x e s r e s p e c t i v e l y ( T a b l e 5 ) . The s t r e a m - t y p e f r y f r o m S l i m 29 F i g u r e 2. Mean a g g r e s s i o n s c o r e s f o r n e w l y - e m e r g e d , w i l d -r e a r e d c h i n o o k s a l m o n f r y i n MIS t e s t s . 2 a = p r i n c i p a l component a x i s 1, 2 b = p r i n c i p a l component a x i s 2. N=25 f o r e a c h p o p u l a t i o n . 2a 2b 31 T a b l e 5. Component c o e f f i c i e n t s d e r i v e d f r o m p r i n c i p a l c o m p o n e n t s a n a l y s i s o f s t r e a m t a n k b e h a v i o u r a l d a t a . B e h a v i o u r C o e f f i c i e n t f r o m PCA Component 1 Component 2 A p p r o a c h 0.496 0.127 L a t e r a l d i s p l a y 0.850 -0.259 Wigwag 0.163 0.956 C h a r g e 0.068 0.019 N i p 0.010 0.031 C h a s e -0.010 0.016 C u m u l a t i v e % t o t a l v a r i a n c e 52.7 89.7 32 C r e e k were more a g g r e s s i v e a l o n g t h e f i r s t a x i s ( 5 5 % o f t o t a l v a r i a t i o n , F i g . 3 a , P = 0.01, d f = 1 , 4 ) and b o t h S l i m a n d H a r r i s o n f r y became more a g g r e s s i v e w i t h t i m e (P=0.05, d f = 4 , l 6 ) . T h e r e was, h o w e v e r , no d i f f e r e n c e i n a g g r e s s i o n l e v e l s b e t w e e n s t r e a m -a n d o c e a n - t y p e f r y a l o n g t h e s e c o n d component a x i s ( 3 4 % t o t a l v a r i a t i o n , F i g . 3b, P = 0 . 1 ) . An i n c r e a s e i n "wigwag" (PC2) d i s p l a y b e h a v i o u r b o t h by S l i m a n d H a r r i s o n c h i n o o k f r y by o b s e r v a t i o n day f o u r s u g g e s t s an i n c r e a s e i n c o m p l e x i t y o f b e h a v i o u r a l d i s p l a y s w i t h t i m e ( w i t h i n f a c t o r " d a y " , P=0.0003, d f = 4 , 1 6 ) . L a b o r a t o r y - r e a r e d f r y When s u b j e c t e d t o PCA, 97% o f t h e b e h a v i o u r a l v a r i a t i o n f r o m t h e MIS t e s t s i n v o l v i n g l a b o r a t o r y - r e a r e d f r y was s u m m a r i z e d by two component a x e s ( T a b l e 6 ) . As was t h e c a s e f o r t h e w i l d - r e a r e d f r y , " s w i m - a g a i n s t - m i r r o r " d o m i n a t e d t h e f i r s t a x i s w h e r e a s " l a t e r a l d i s p l a y " b e h a v i o u r d o m i n a t e d t h e s e c o n d ( T a b l e 6 ) . A l o n g component a x i s 1, S l i m C r e e k f r y were more a g g r e s s i v e t h a n E a g l e R i v e r f r y , b u t f r y o f b o t h t h e s e s t r e a m -t y p e p o p u l a t i o n s were more a g g r e s s i v e t h a n t h e o c e a n - t y p e f r y f r o m t h e Nanaimo a n d H a r r i s o n r i v e r s ( F i g . 4 a , P=0.0001, d f = 3 , 9 6 ) . A l t h o u g h t h e t r e n d was l e s s m a r k e d t h a n i n t h e w i l d f r y MIS t e s t s , a s l i g h t t r e n d t o w a r d s i n c r e a s i n g r e s p o n s i v e n e s s w i t h t i m e was e v i d e n t i n t h e l a b o r a t o r y - r e a r e d f r y ( d a y f a c t o r , P=0.02, d f = 6 , 4 5 0 ) . A l o n g component a x i s 2 S l i m C r e e k f r y were t h e most a g g r e s s i v e ( i . e . h i g h e s t mean PC s c o r e s ) , Nanaimo 33 F i g u r e 3. Mean a g g r e s s i o n s c o r e s f o r n e w l y - e m e r g e d , w i l d -r e a r e d c h i n o o k s a l m o n f r y i n s t r e a m t a n k t e s t s . 3 a = p r i n c i p a l component a x i s 1, 3 b = p r i n c i p a l component a x i s 2. N=3 g r o u p s o f 16 f r y p e r p o p u l a t i o n . 3a 3b 35 T a b l e 6. Component c o e f f i c i e n t s d e r i v e d f r o m p r i n c i p a l c o m p o n e n t s a n a l y s i s o f MIS b e h a v i o u r a l d a t a o f l a b o r a t o r y -r e a r e d c h i n o o k f r y . C o e f f i c i e n t f r o m PCA B e h a v i o u r Component 1 Component 2 A p p r o a c h S w i m - a g a i n s t - m i r r o r L a t e r a l d i s p l a y Wigwag -0.004 0.999 0.039 0.022 0.019 -0.043 0.952 0.299 C u m u l a t i v e % t o t a l v a r i a n c e 89.1 97.3 36 F i g u r e 4. Mean a g g r e s s i o n s c o r e s f o r n e w l y - e m e r g e d , l a b o r a t o r y - r e a r e d c h i n o o k s a l m o n f r y i n MIS t e s t s . 4 a = p r i n c i p a l component a x i s 1, 4 b = p r i n c i p a l component a x i s 2. N=25 f r y p e r p o p u l a t i o n . "i i i i i 1 1 — 1 — i 1 1 1 1 r 1 2 3 4 5 6 7 1 2 3 4 5 6 OBSERVATION DAY OBSERVATION DAY • SLIM CREEK • EAGLE RIVER • I^NAjMORIVER O HARRISON RIVER co 38 R i v e r , o c e a n - t y p e f r y were t h e l e a s t a g g r e s s i v e , a n d H a r r i s o n and E a g l e r i v e r s f r y were i n t e r m e d i a t e ( F i g . 4b, P = 0 . 0 0 0 1 ) . S t r e a m t a n k i n t e r a c t i o n d a t a s u m m a r i z e d by PCA p r o d u c e d t h r e e component a x e s ( 9 7 % o f t o t a l v a r i a t i o n ) d o m i n a t e d by "wigwag", " l a t e r a l d i s p l a y " , a n d " a p p r o a c h " b e h a v i o u r s r e s p e c t i v e l y ( T a b l e 7 ) . A l o n g component a x i s 1 ( 5 8 % o f t o t a l v a r i a n c e ) s t r e a m - t y p e f r y f r o m S l i m C r e e k a nd E a g l e R i v e r were c l e a r l y more a g g r e s s i v e t h a n t h e o c e a n - t y p e f r y f r o m H a r r i s o n a n d Nanaimo r i v e r s ( F i g . 5 a , P=0.0001, d f = 3 , 8 ) w i t h l i t t l e c o n s i s t e n t c h a n g e w i t h t i m e ( d ay f a c t o r , P=0.9, d f = 4 , 3 2 ) . Component a x i s 2, c o n t r a s t e d " l a t e r a l d i s p l a y " w i t h t h e more e l a b o r a t e "wigwag" d i s p l a y ( T a b l e 7 ) . A l o n g component a x i s 2 ( F i g . 5 b ) , t h e p o p u l a t i o n s f e l l i n t o t h r e e g r o u p s b a s e d on t h e i r mean PC s c o r e s . S l i m C r e e k f r y had t h e h i g h e s t mean s c o r e i n d i c a t i n g h i g h l e v e l s o f " l a t e r a l d i s p l a y " b e h a v i o u r , o c e a n -t y p e f r y f r o m H a r r i s o n a n d Nanaimo r i v e r s h a d i n t e r m e d i a t e s c o r e s , a n d E a g l e R i v e r , s t r e a m - t y p e f r y h a d t h e l o w e s t mean s c o r e . The l o w mean PC s c o r e o f E a g l e R i v e r c h i n o o k f r y r e s u l t e d f r o m h i g h l e v e l s o f "wigwag" d i s p l a y b e h a v i o u r s on o b s e r v a t i o n d a y s 2 a n d 3 ( F i g . 5 b ) . The component c o e f f i c i e n t f o r "wigwag" on component a x i s 2 i s r e a s o n a b l y h i g h a n d o p p o s i t e i n s i g n t o t h a t f o r " l a t e r a l d i s p l a y " (-0.47, T a b l e 7) a n d E a g l e R i v e r f r y h a d h i g h n e g a t i v e PC s c o r e s e a r l y d u r i n g t h e t e s t p e r i o d ( F i g . 5b) w h i c h d e c l i n e d a s t h e t e s t s p r o c e e d e d . T h e r e f o r e , a t l e a s t e a r l y i n t h e t e s t p e r i o d , b o t h S l i m a n d 39 T a b l e 7. Component c o e f f i c i e n t s d e r i v e d f r o m p r i n c i p a l c o m p o n e n t s a n a l y s i s o f s t r e a m t a n k b e h a v i o u r a l d a t a f o r l a b o r a t o r y - r e a r e d c h i n o o k f r y . B e h a v i o u r C o e f f i c i e n t f r o m PCA Component 1 Component 2 Component 3 A p p r o a c h 0.500 0.231 -0.831 L a t e r a l d i s p l a y 0.307 0.837 0.398 Wigwag 0.807 -0.473 0.351 C h a r g e 0.064 0.115 0.1 37 N i p 0.016 0.097 0.092 C h a s e 0.002 0.004 -0.009 C u m u l a t i v e % t o t a l v a r i a n c e 58.5 87.9 96.7 40 F i g u r e 5. Mean stream tank a g g r e s s i o n scores f o r l a b o r a t o r y -rearded chinook f r y . 5 a = p r i n c i p a l component a x i s 1, 5 b = p r i n c i p a l component a x i s 2, 5 c = p r i n c i p a l component a x i s 3. N=3 groups of 16 f r y per p o p u l a t i o n . MEAN PC1 SCORE o CD CO m 70 5 Ol (Jl o I O I o I o> o 00 o o o o I Q MEAN PC2 SCORE o CD CO m 70 5 N> cn o i i M O I O I M O O cr MEAN PC3 SCORE o CD CO > cn i CH o i I ro cn i I M O _L_ O I o I cn o o • X l z ' n > >> > Z o l> (— n 00 3^ o l O z '=0 < m | < ;o < m l m X) 00 42 E a g l e , s t r e a m - t y p e c h i n o o k s were t h e most a g g r e s s i v e f r y , b u t i n t e r m s o f d i f f e r e n t b e h a v i o u r s - l a t e r a l d i s p l a y f o r S l i m C r e e k c h i n o o k a n d wigwag f o r E a g l e f r y . By c o n t r a s t , no t r e n d was a p p a r e n t i n d i s p l a y b e h a v i o u r s f o r H a r r i s o n o r Nanaimo r i v e r c h i n o o k f r y ; b o t h h ad s i m i l a r i n t e r m e d i a t e p o s i t i v e PC s c o r e s t h r o u g h o u t t h e 5 day t e s t p e r i o d . Component a x i s 3 was d o m i n a t e d by " a p p r o a c h " , b u t a l s o s e r v e d t o c o n t r a s t t h i s o v e r t b e h a v i o u r w i t h a g g r e s s i o n e x p r e s s e d t h r o u g h d i s p l a y b e h a v i o u r s ( T a b l e 7 ) . The p o p u l a t i o n s a g a i n t e n d e d t o d i v e r g e i n t o two g r o u p s b a s e d on mean PC s c o r e s ; S l i m C r e e k a n d E a g l e R i v e r s t r e a m - t y p e f r y h a d h i g h e r n e g a t i v e s c o r e s ( i . e . t h e y were more a g g r e s s i v e i n t e r m s o f " a p p r o a c h " ) t h a n H a r r i s o n a nd Nanaimo f r y . The o n l y s i g n i f i c a n t d i f f e r e n c e s , h o w e v e r , were b e t w e e n S l i m C r e e k f r y a n d f r y f r o m t h e o c e a n - t y p e p o p u l a t i o n s , H a r r i s o n a n d Nanaimo r i v e r s ( F i g . 5 c , P < 0 . 0 0 1 ) . To s u m m a r i z e , b o t h w i l d a n d l a b o r a t o r y - r e a r e d s t r e a m - t y p e c h i n o o k s a l m o n f r y were c o n s i s t e n t l y more a g g r e s s i v e t h a n t h e e a r l i e r m i g r a t i n g , o c e a n - t y p e c h i n o o k f r y . W i t h i n t h e s e b r o a d j u v e n i l e l i f e h i s t o r y c a t e g o r i e s , S l i m C r e e k s t r e a m - t y p e f r y were t h e most a g g r e s s i v e w h i l e H a r r i s o n R i v e r , o c e a n - t y p e c h i n o o k were u s u a l l y t h e l e a s t a g g r e s s i v e . 43 C. M o r p h o l o g y a n d c o l o u r a t i o n W i l d f r y S l i m C r e e k , s t r e a m - t y p e c h i n o o k f r y h a d l a r g e r body p a r t s a n d m e d i a n f i n s t h a n o c e a n - t y p e f r y o f t h e same s i z e f r o m t h e H a r r i s o n R i v e r . Body d e p t h , h e a d d e p t h , d o r s a l f i n h e i g h t , c a u d a l f i n d e p t h , a n d maximum p a r r mark l e n g t h showed s i g n i f i c a n t d i f f e r e n c e s ( T a b l e 8). S l i m C r e e k f r y a l s o h a d more p a r r m a r k i n g s a n d more e l a b o r a t e body c o l o u r a t i o n ( an o r a n g e s t r i p e a l o n g t h e l o w e r jaw a n d b r i g h t o r a n g e - b l a c k c o l o u r a t i o n on t h e c a u d a l f i n ) . T h i s c o l o u r a t i o n was a p p a r e n t when f r y were f i r s t c o l l e c t e d a n d p e r s i s t e d d u r i n g r e a r i n g i n t h e l a b o r a t o r y ( a b o u t 2 m o n t h s ) . S l i m C r e e k c h i n o o k were p r o m i n e n t l y p i g m e n t e d a t t h e b e g i n n i n g o f t h e s t r e a m t a n k b e h a v i o u r t e s t s . By c o n t r a s t , H a r r i s o n R i v e r , o c e a n - t y p e f r y i n i t i a l l y h a d t r a n s p a r e n t m e d i a n f i n s . By t h e end o f t h e s t r e a m t a n k e x p e r i m e n t s , h o w e v e r , some H a r r i s o n R i v e r f r y h a d d e v e l o p e d p r o m i n e n t m a r k i n g s on t h e i r m e d i a n f i n s c o n s i s t i n g o f b l a c k l e a d i n g e d g e s w i t h w h i t e t i p s a n d some y e l l o w / b l a c k c o l o u r a t i o n on t h e c a u d a l f i n . 44 T a b l e 8. M o r p h o l o g i c a l c o m p a r i s o n o f w i l d - r e a r e d , n e w l y -emerged c h i n o o k s a l m o n f r y . Body p r o p o r t i o n s a r e means (SE) a d j u s t e d t o a s t a n d a r d l e n g t h o f 34 mm by c o v a r i a n c e a n a l y s i s ; N=30 f o r e a c h p o p u l a t i o n , * P<0.05, **P < 0.01, ***P < 0.001 f o r d f = 1 , 5 7 . C h a r a c t e r S l i m C r e e k H a r r i s o n R i v e r S t a n d a r d l e n g t h 31 .2 ( 0 . 1 8 ) 34.9 ( 0 . 3 2 ) Body p r o p o r t i o n s Body d e p t h * 5.8 ( 0 . 0 7 ) 5.4 ( 0 . 0 5 ) Head d e p t h * 5.5 ( 0 . 0 5 ) 5.3 ( 0 . 0 5 ) Head l e n g t h 9.5 ( 0 . 0 8 ) 9.4 ( 0 . 0 8 ) D o r s a l f i n h e i g h t * 4.2 ( 0 . 0 6 ) 3.8 ( 0 . 0 9 ) D o r s a l f i n l e n g t h 6.7 ( 0 . 0 8 ) 6.5 ( 0 . 0 9 ) A n a l f i n h e i g h t 3.7 ( 0 . 0 8 ) 3.6 ( 0 . 0 8 ) A n a l f i n l e n g t h 5.3 ( 0 . 0 4 ) 5.1 ( 0 . 0 4 ) C a u d a l f i n d e p t h * 1 9.0 ( 0 . 1 0 ) 7.8 ( 0 . 1 2 ) Maximum p a r r mark l e n g t h * 3.5 ( 0 . 1 0 ) 3.1 ( 0 . 1 0 ) Maximum p a r r mark w i d t h 1.7 ( 0 . 0 6 ) 1.8 ( 0 . 0 6 ) C o u n t s No. m a j o r p a r r m a r k s * * 10.7 ( 0 . 2 5 ) 9.6 ( 0 . 2 5 ) No. t o t a l p a r r m a r k s * * * 23.8 ( 0 . 8 4 ) 15.2 ( 0 . 8 4 ) 1 - h e t e r o g e n o u s s t a n d a r d l e n g t h - c h a r a c t e r r e g r e s s i o n s l o p e s (P<0.05, d f = 1 , 5 6 ) . 45 L a b o r a t o r y - r e a r e d f r y M o r p h o l o g i c a l a n a l y s i s suggested no c o n s i s t e n t stream/ocean-type dichotomy w i t h r e s p e c t t o body form or c o l o u r a t i o n among the l a b o r a t o r y - r e a r e d f r y from the f o u r p o p u l a t i o n s (Table 9). A l t h o u g h stream-type c h i n o o k from S l i m Creek and the E a g l e R i v e r had the deepest b o d i e s and heads, i t was S l i m Creek f r y and o c e a n -type, Nanaimo R i v e r f r y t h a t had the l a r g e s t median f i n s . In f a c t , a l t h o u g h S l i m Creek f r y c o n s i s t e n t l y had the l a r g e s t f i n s , i n a l l but one f i n measurement ( a f l ) E a g l e R i v e r , stream-type f r y had the s m a l l e s t f i n s . The p o p u l a t i o n s a l s o d i f f e r e d i n the number of p a r r marks, but. a g a i n t h e r e was no d i s t i n c t i o n between stream- and ocean-type salmon; Nanaimo and E a g l e r i v e r f r y had the most major and t o t a l p a r r marks (T a b l e 9). A l l f r y p o s s e s s e d b l a c k and w h i t e l e a d i n g edges on the d o r s a l f i n and w h i t e t i p s on t h e i r a n a l f i n s . As was the case f o r the w i l d - r e a r e d f r y , the g r e a t e s t d i s t i n c t i o n w i t h r e s p e c t t o f i n c o l o u r a t i o n was i n the degree of orange pigment i n the median and p a i r e d f i n s . S l i m Creek f r y were the most e l a b o r a t e l y c o l o u r e d , they had prominent orange c o l o u r a t i o n on a l l median and p a i r e d f i n s . Nanaimo R i v e r f r y were a l s o w e l l c o l o u r e d , but they l a c k e d the b r i g h t o r a n g e - b l a c k c o l o u r on the c a u d a l f i n and orange c o l o u r a t i o n on the p a i r e d f i n s shown by S l i m f r y . Stream-type f r y from the E a g l e R i v e r tended t o be 46 Tab le 9. Mean (SE) s t a n d a r d l e n g t h , body p r o p o r t i o n s i n mm, and p a r r mark c o u n t s f o r new 1y-emerged , l a b o r a t o r y ch inook salmon f r y f rom the s t u d y p o p u l a t i o n s . N=30 in a l l cases and measurements were a d j u s t e d t o an o v e r a l l sample mean s t a n d a r d l e n g t h o f 30 .6 mm by c o v a r i a n c e a n a l y s i s . The i n d i c a t e d p r o b a b i l i t y i s t h a t a l l a d j u s t e d means a re the same ( d f = 3 . 1 1 5 ) . C h a r a c t e r S l i m Cr . Eagle R. Nanaimo R. H a r r i s o n R. P S t a n d a r d l e n g t h 30. , 5 (0 . , 22) 28. ,6 ( 0 , ,20) 32. 7 (0 , ,29) 31 . , 2 ( 0 . , 16) Body p r o p o r t i o n s Body d e p t h 6 ; . 3 (0 . ,06) 6 , 4 ( 0 , ,08) 5. 7 (0 .08) 5 , 9 ( 0 , 06) < 0, ,001 Head d e p t h * 5. . 8 (0 .05) 5, .5 ( 0 , ,06) 5. 4 (0 .06) 5, , 4 (0 , ,05) < 0, ,001 Head l e n g t h * 8. .6 (0 .05) 8, , 2 ( 0 , .07) 8. 5 (0 , ,07) 8 , 6 ( 0 , ,05) < 0, ,001 D o r s a l f i n h e i g h t 3. . 7 (0 .07) 2 . 8 ( 0 , ,09) 3. 1 (0 .09) 2 , 9 (0 , ,07) < 0, ,001 D o r s a l f i n l e n g t h 6 . 3 ( 0 . .07) 5. , 2 ( 0 , .09) 5. 7 (0 . ,09) 5 , . 8 ( 0 , ,07) < 0, ,001 Ana 1 f i n he i g h t 3, . 5 (0 . .05) 2, ,8 ( 0 , ,07) 3, 0 (0 .07) 2, , 9 (0 , .05) < 0 ,001 Anal f i n l e n g t h . 4. 8 ( 0 . .09) 4 , .2 ( 0 , . 12) 4 . 2 (0 .11) 4 , . 4 (0 ,09) < 0 .001 Caudal f i n d e p t h * 7 . 7 (0 . . 14) 7 . 5 ( 0 , . 18) 7 . 6 (0 . 18) 7 , . 5 to .14) > 0 .05 Par r mark l e n g t h 3. . 1 (0 . .11) 2 .6 (0 . 14) 2. ,5 (0 . 13) 2 .8 (0 . 10) < 0 .005 Par r mark w i d t h 1 . . 8 (0 . .04) 1 . . 4 ( 0 , ,05) 1 . 3 (0 .05) 1 , , 3 ( 0 , ,04) < 0 ,001 Counts No. ma jo r p a r r marks 9 . 2 ( 0 . .21 ) 10, ,6 ( 0 , , 29) 11 . 4 to. . 28) 10 . , 1 ( 0 . , 22) < 0 ,00 1 No. t o t a l p a r r marks 15. . 7 ( 0 . ,73) 18, . 4 (O. ,97) 21 . , 1 (0 .93) 15 . 1 ( 0 , .74) < 0 .001 • h e t e r o g e n o u s s t a n d a r d l e n g t h - c h a r a c t e r r e g r e s s i o n s l o p e s (p < 0 . 0 5 , d f = 3 , 1 1 2 ) 4 7 l i g h t e r i n c o l o u r t h a n f r y f r o m e i t h e r S l i m C r e e k o r t h e Nanaimo R i v e r . A l t h o u g h E a g l e R i v e r c h i n o o k f r y h a d o r a n g e p i g m e n t on t h e i r m e d i a n f i n s i t was n o t u n i v e r s a l , e s p e c i a l l y on t h e c a u d a l f i n . I n a d d i t i o n , many E a g l e f r y l a c k e d t h e o r a n g e m a n d i b l e s t r i p e c h a r a c t e r i s t i c o f t h e S l i m C r e e k a n d Nanaimo R i v e r f r y . The H a r r i s o n R i v e r , o c e a n - t y p e f r y were t h e l e a s t b r i g h t l y c o l o u r e d ; t h e y l a c k e d any t r a c e o f o r a n g e p i g m e n t i n t h e i r f i n s , a l t h o u g h some f a i n t y e l l o w c o l o u r was p r e s e n t on t h e c a u d a l f i n . 48 2. INTER-, INTRAPOPULATION, AND TEMPORAL VARIATION I N BEHAVIOUR AND GROWTH OF J U V E N I L E CHINOOK SALMON M e t h o d s E x p e r i m e n t a l a n i m a l s The e x p e r i m e n t a l f i s h were p r o g e n y o f a d u l t s a l m o n f r o m e i g h t p o p u l a t i o n s i n B r i t i s h C o l u m b i a c o l l e c t e d d u r i n g t h e autumn o f 1986 ( T a b l e 1 0 ) , f o u r were were s t r e a m - t y p e a n d f o u r o c e a n - t y p e . They were c l a s s i f i e d u s i n g f i e l d o b s e r v a t i o n s o f j u v e n i l e d o w n s t r e a m m i g r a t i o n t i m i n g a n d t h e p r e s e n c e o f a f r e s h w a t e r a n n u l u s on a d u l t s c a l e s ( H e a l e y a n d J o r d a n 1982; C a r l a n d H e a l e y 1984; S h e p h e r d e t a l . 1 9 8 6 a ) . A d u l t s a l m o n were c o l l e c t e d by s e i n i n g , d r i f t n e t t i n g , o r f r o m f e n c e s a s s o c i a t e d w i t h e nhancement f a c i l i t i e s . I n a l l c a s e s , g a m e t e s f r o m a number o f m a l e s a n d f e m a l e s ( T a b l e 10) were o b t a i n e d a n d f e r t i l i z a t i o n was c o m p l e t e d i n t h e f i e l d a s o u t l i n e d p r e v i o u s l y ( p p . 1 3 - 1 4 ) . Z y g o t e s were t r a n s p o r t e d t o t h e l a b o r a t o r y a t t h e U n i v e r s i t y a n d i n c u b a t e d a t 8 C. The embryos a n d l a r v a e were i n c u b a t e d i n d a r k n e s s f o r a p p r o x i m a t e l y 6 months a t a w a t e r f l o w o f 2 L / m i n . A t e m e r g e n c e , a p p r o x i m a t e l y 1,500 f r y f r o m e a c h p o p u l a t i o n were r a n d o m l y a s s i g n e d t o one o f e i g h t 94 L f i b e r g l a s s r e a r i n g t r o u g h s . R e a r i n g c o n d i t i o n s were a s d e s c r i b e d e a r l i e r ( 1 . 1 ) . 49 T a b l e 10. Number o f m a l e and f e m a l e p a r e n t s u s e d i n e x p e r i m e n t a l c r o s s e s o f c h i n o o k s a l m o n f r o m s t r e a m - and o c e a n - t y p e p o p u l a t i o n s . No. m a l e s P o p u l a t i o n x no. f e m a l e s S t r e a m - t y p e Bowron R i v e r 10 X 10 S l i m C r e e k 6 X 7 E a g l e R i v e r 5 X 5 S a l mon R i v e r 5 X 3 O c e a n - t y p e L i t t l e Q u a l i c u m R i v e r 4 X 5 H a r r i s o n R i v e r 5 X 5 Nanaimo R i v e r ( l o w e r ) 10 X 10 Nanaimo R i v e r ( 1 s t l a k e ) 8 X 6 50 The g r o w i n g s a l m o n were t r a n s f e r r e d t o 900 L, o v a l r e a r i n g t a n k s a t 3 months o f age where p h o t o p e r i o d and w a t e r f l o w c o n d i t i o n s w ere i d e n t i c a l t o t h o s e i n t h e r e a r i n g t r o u g h s . A. I n t e r - , i n t r a p o p u l a t i o n , a n d t e m p o r a l v a r i a t i o n i n  r h e o t a c t i c b e h a v i o u r C u r r e n t r e s p o n s e was t e s t e d f o r j u v e n i l e s a l m o n a t " s p r i n g " t h r o u g h " l a t e summer" ( e m e r g e n c e , 1, 2, 3 a n d 4 m o n t h s ) , " f a l l " (6 m o n t h s ) , " w i n t e r " (9 m o n t h s ) , a n d 1 y e a r f o l l o w i n g e m e r g e n c e (12 m o n t h s ) . T h e s e t e s t s were r u n o v e r a f u l l y e a r t o d e t e c t d i f f e r e n c e s among p o p u l a t i o n s t h a t m i g h t c o r r e s p o n d t o m a j o r p e r i o d s o f j u v e n i l e s e a w a r d m i g r a t i o n o t h e r t h a n a t e mergence ( i . e . 2-4 months i n o c e a n - t y p e c h i n o o k o r 1 y e a r i n s t r e a m - t y p e c h i n o o k ) . The t e s t s were r u n i n t h e two o v a l - s h a p e d s t r e a m c h a n n e l s d e s c r i b e d e a r l i e r ( 1 . 1 ) . The c h a n n e l s t r u c t u r e a n d t e s t p r o t o c o l were m o d i f i e d s l i g h t l y t o a c c o u n t f o r t h e i n c r e a s i n g s i z e o f f i s h w i t h a g e . B o t h c h a n n e l s were s u b d i v i d e d i n t o 13 c o m p a r t m e n t s r a n k e d f r o m -6 (most d o w n s t r e a m ) t h r o u g h 0 ( c e n t r a l c o m p a r t m e n t ) t o +6 (most u p s t r e a m ) . E a c h c o m p a r t m e n t (30 x 30 x 25 cm) was c o n n e c t e d t o a d j a c e n t c o m p a r t m e n t s by h o l e s ( 4 . 5 cm d i a m e t e r ) i n t h e c o m p a r t m e n t w a l l s . The h o l e s i n s u c c e s s i v e c o m p a r t m e n t w a l l s were s t a g g e r e d " s i d e - t o - s i d e " s o t h a t t h e s a l m o n h a d t o " s e a r c h " f o r t h e o p e n i n g s a s t h e y moved u p s t r e a m o r d o w n s t r e a m . E a c h t e s t a s s e s s e d t h e movements o f 15 f i s h 51 t h r o u g h t h e c o m p a r t m e n t s d u r i n g a 3 h p e r i o d u n d e r s i m u l a t e d n o c t u r n a l a n d d i u r n a l c o n d i t i o n s . The e v e n i n g b e f o r e a t e s t , 15 f r y were p l a c e d i n t h e c e n t r a l c o m p a r t m e n t w i t h t h e e x i t a n d e n t r a n c e h o l e s c l o s e d . Commencing a t a b o u t m i d - d a y t h e f o l l o w i n g day t h e t e s t s were i n i t i a t e d a s d e s c r i b e d e a r l i e r ( 1 . 1 ) . A t e a c h a g e , e i g h t d i u r n a l a n d e i g h t n o c t u r a l t e s t s were r u n on e a c h p o p u l a t i o n . F o r e a c h t e s t , a "movement s c o r e " was c a l c u l a t e d by summing t h e p r o d u c t s o f t h e number o f f i s h i n e a c h c o m p a r t m e n t a n d t h e r a n k o f t h a t c o m p a r t m e n t t h e n d i v i d i n g by 15, t h e number o f f i s h i n e a c h t e s t . A c o n s t a n t o f 6 was a d d e d t o e l i m i n a t e n e g a t i v e o s c o r e s . W a t e r t e m p e r a t u r e was m a i n t a i n e d b e t w e e n 10-10.5 C f o r a l l t e s t s a n d w a t e r v e l o c i t y t h r o u g h t h e c o m p a r t m e n t o p e n i n g s a v e r a g e d a b o u t 10 cm/s. B. I n t e r - , i n t r a p o p u l a t i o n , a n d t e m p o r a l v a r i a t i o n i n  a g g r e s s i v e b e h a v i o u r T e s t f i s h a t 5 a g e s : e m e r g e n c e , 1, 2, 3, a n d 6 months o f age were f r o m S l i m C r e e k ( s t r e a m - t y p e ) a n d two Nanaimo R i v e r p o p u l a t i o n s . One p o p u l a t i o n ( " 1 s t L a k e , F i g . 6) spawns a b o u t 20 km u p s t r e a m o f t h e e s t u a r y a t t h e o u t l e t o f 1 s t L a k e a n d most o f i t s j u v e n i l e s m i g r a t e s e a w a r d a f t e r 2-3 months i n f r e s h w a t e r ( C a r l a n d H e a l e y 1 9 8 4 ) . The s e c o n d p o p u l a t i o n ( " l o w e r r i v e r " ) spawns a b o u t 5-10 km u p s t r e a m o f t h e e s t u a r y a n d i t s f r y m i g r a t e t o t h e e s t u a r y w i t h i n a few d a y s o f e m e r g e n c e ( C a r l a n d H e a l e y 52 F i g u r e 6. M a j o r f e a t u r e s o f t h e Nanaimo R i v e r i n c l u d i n g s p a w n i n g a r e a s ( s t i p p l i n g ) o f "Lower N a n a i m o " (A) a n d " 1 s t L a k e " (B) p o p u l a t i o n s o f c h i n o o k s a l m o n i n t h e r i v e r . L o c a t i o n o f Nanaimo t o w n s i t e i s i n d i c a t e d by t h e open s t a r . Redrawn f r o m H e a l e y a n d J o r d a n ( 1 9 8 2 ) . cn to 54 1 9 8 4 ) . The number and d u r a t i o n o f a g g r e s s i v e b e h a v i o u r s d u r i n g o m u l t i p l e f r y , s t r e a m t a n k t e s t s (10 C) were r e c o r d e d u s i n g m e t h o d o l o g y m o d i f i e d s l i g h t l y f r o m t h a t d e s c r i b e d e a r l i e r ( 1 . 1 ) . The b o t t o m s o f s t r e a m t a n k s e c t i o n s were c o v e r e d w i t h g r a v e l t o a d e p t h o f a b o u t 4 cm. E i g h t s m a l l s t o n e s , a b o u t 5 cm d i a m e t e r , f o r m e d a z i g - z a g p a t t e r n a l o n g t h e b o t t o m t o s e r v e a s r e f e r e n c e p o i n t s f o r t h e f i s h . I n f l o w i n g d e c h l o r i n a t e d w a t e r was s e t t o 2.5 L / m i n a n d w a t e r v e l o c i t y t o 6-7 cm/s f o r t e s t s r u n a t e m e r g e n c e and 1 month o f a g e . T h e r e a f t e r , a w a t e r v e l o c i t y o f 10 cm/s e n s u r e d u p s t r e a m o r i e n t a t i o n i n t h e o l d e r ( a n d l a r g e r ) t e s t f i s h . The s t r e a m t a n k s were e n c l o s e d w i t h i n b l a c k p l a s t i c s h e e t i n g w i t h o b s e r v a t i o n h o l e s , a n d p h o t o p e r i o d f o l l o w e d t h e s e a s o n a l c y c l e . F o r e a c h p o p u l a t i o n a t e a c h a g e , t e n f i s h were a l l o w e d t o a d j u s t i n e a c h o f t h r e e s t r e a m t a n k s e c t i o n s f o r 48 h. T h e r e a f t e r , t h e number a n d d u r a t i o n o f a g g r e s s i v e b e h a v i o u r s were r e c o r d e d i n e a c h s e c t i o n f o r 10 min a t 09:00 a n d 17:00 f o r f i v e c o n s e c u t i v e d a y s . The b e h a v i o u r s r e c o r d e d w e r e : " n u l l " , " a p p r o a c h " , " l a t e r a l d i s p l a y " , "wigwag", " c h a r g e " , a nd " n i p " ( T a b l e 1 ) . F i s h were f e d a f t e r e a c h o b s e r v a t i o n p e r i o d , a nd a t m i d - d a y , a t a b o u t 5% bw/d. A t e m e r g e n c e and 1 month o f age t h e y were f e d l i v e b r i n e s h r i m p ( A r t e m i a s a l i n a ) n a u p l i i , a n d a t o l d e r a g e s t h e y were f e d l i v e , a d u l t s h r i m p . 55 C. V a r i a t i o n i n g r o w t h r a t e ' G r o w t h o f c h i n o o k was m o n i t o r e d by s t a n d a r d l e n g t h ( S L ) , f o r k l e n g t h ( F L , R i c k e r ( 1 9 7 9 ) ) , a n d w e i g h t m e a s u r e m e n t s o f a random s a m p l e o f 30 i n d i v i d u a l s f r o m e a c h p o p u l a t i o n a t m o n t h l y i n t e r v a l s . I n d i v i d u a l s were l i g h t l y a n a e s t h e s i z e d w i t h 2-p h e n o x y e t h a n o l , b l o t t e d on a m o i s t p a p e r t o w e l , m e a s u r e d a nd w e i g h e d t o t h e n e a r e s t 0.5 mm and 0.01 g r e s p e c t i v e l y . S p e c i f i c g r o w t h r a t e s (SGR) were c a l c u l a t e d a s : SGR = l n ( W f / W i ) • 1 00-d"', where Wf a n d Wi a r e t h e f i n a l a n d i n i t i a l mean wet w e i g h t s o v e r t h e t i m e p e r i o d d, i n d a y s , f o r e a c h p o p u l a t i o n ( C l a r k e a n d S h e l b o u r n 1 9 8 6 ) . To p r o m o t e maximum g r o w t h r a t e s w i t h c h a n g i n g t e m p e r a t u r e a n d b i o m a s s , f i s h were f e d t h r e e t i m e s p e r day on a s c h e d u l e o f p e l l e t s i z e s a n d r a t i o n l e v e l s recommended by t h e m a n u f a c t u e r ( M o o r e - C l a r k e L t d . , L a C o n n e r , W a s h i n g t o n ) . D. S t a t i s t i c a l a n a l y s i s D a t a f r o m t h e c u r r e n t r e s p o n s e t e s t s r u n u n d e r d i u r n a l a n d n o c t u r n a l c o n d i t i o n s were a n a l y z e d s e p a r a t e l y by f a c t o r i a l , n e s t e d a n a l y s i s o f v a r i a n c e . Age a n d l i f e h i s t o r y t y p e ( o c e a n -o r s t r e a m - t y p e ) were t h e f i x e d , m a i n e f f e c t s a n d p o p u l a t i o n was c o n s i d e r e d a s a random e f f e c t n e s t e d w i t h i n l i f e h i s t o r y t y p e . To d e t e r m i n e i f t h e mean movement s c o r e s f o r e a c h p o p u l a t i o n a t 56 e a c h age were s i g n i f i c a n t l y d i f f e r e n t f r o m 6 ( i . e . a s c o r e o f 6 = no s i g n i f i c a n t u p s t r e a m o r d o w n s t r e a m movement), t - t e s t s were u s e d w i t h t h e l e v e l o f s i g n i f i c a n c e a d j u s t e d t h r o u g h d i v i s i o n by t h e number o f t e s t s . D a t a on t h e d u r a t i o n o f a g g r e s s i v e b e h a v i o u r s were s u m m a r i z e d by p r i n c i p a l c o m p o n e n t s a n a l y s i s (PCA) a s d e s c r i b e d e a r l i e r . S u b s e q u e n t l y , I a n a l y z e d t h e PC s c o r e s u s i n g f a c t o r i a l , r e p e a t e d m e a s u r e s a n a l y s i s o f v a r i a n c e ; age a n d p o p u l a t i o n were t h e m a i n e f f e c t s . G r o w t h r a t e was a n a l y z e d by r e g r e s s i n g SGR on age a n d c o m p a r i n g g r o w t h r a t e s among p o p u l a t i o n s a n d l i f e h i s t o r y t y p e s a t a common age by n e s t e d , a n a l y s i s o f c o v a r i a n c e . A g a i n , l i f e h i s t o r y t y p e was t h e m a i n , f i x e d e f f e c t a n d p o p u l a t i o n c o n s i d e r e d a s t h e random e f f e c t n e s t e d w i t h i n l i f e h i s t o r y t y p e , a n d age was t h e c o v a r i a t e . I n a l l s t a t i s t i c a l t e s t s , d i f f e r e n c e s among g r o u p means were a s s e s s e d u s i n g T u k e y ' s t e s t a n d v a r i a n c e h o m o g e n e i t y was v e r i f i e d by B a r t l e t t ' s t e s t . No b e h a v i o u r a l o r g r o w t h r a t e d a t a w e re a v a i l a b l e f r o m L i t t l e Q u a l i c u m a n d l o w e r Nanaimo p o p u l a t i o n s a f t e r f o u r months due t o >80% l o s s e s f r o m c h l o r i n e i n t h e m u n i c i p a l w a t e r s u p p l y . 57 R e s u l t s A. I n t e r - , i n t r a p o p u l a t i o n , a n d t e m p o r a l v a r i a t i o n i n  r h e o t a c t i c b e h a v i o u r U n d e r s i m u l a t e d n o c t u r n a l c o n d i t i o n s , s t r e a m - t y p e c h i n o o k h a d a l o w e r mean n e t movement s c o r e ( i . e . t h e y moved d o w n s t r e a m more) o v e r t h e 1 y e a r p e r i o d t h a n o c e a n - t y p e c h i n o o k ( F i g . 7, P < 0.05, d f = 1 , 6 ) . As w e l l , p o p u l a t i o n s v a r i e d s i g n i f i c a n t l y w i t h i n s t r e a m - a nd o c e a n - t y p e l i f e h i s t o r y g r o u p i n g s (P < 0.001, d f = 6 , 4 1 2 , T a b l e 1 1 ) . M o s t o f t h e v a r i a t i o n i n movement s c o r e s was a t t r i b u t a b l e t o age ( 5 0 % , P < 0.0001, d f = 7 , 3 6 , F i g . 7 ) . Do w n s t r e a m movement o c c u r r e d p r i m a r i l y a t e m e r g e n c e , 1, 2, and 12 m o n t h s ; l i t t l e movement was e v i d e n t b e t w e e n 3 a n d 9 m o n t h s . The e f f e c t o f age on d o w n s t r e a m movement s c o r e s was, h o w e v e r , i n f l u e n c e d by l i f e h i s t o r y t y p e (age X l i f e h i s t o r y i n t e r a c t i o n P < 0.0001, d f = 7 , 3 6 , F i g . 7 ) . S t r e a m - t y p e c h i n o o k moved d o w n s t r e a m t o a g r e a t e r e x t e n t up t o 2 months ( P < 0 . 0 5 ) , b u t movement s c o r e s were most s i m i l a r b e t w e e n s t r e a m - a n d o c e a n -t y p e c h i n o o k b e t w e e n 4 and 9 months ( F i g . 7 ) . By 12 m o n t h s , h o w e v e r , s t r e a m - t y p e c h i n o o k a g a i n showed s i g n i f i c a n t l y g r e a t e r d o w n s t r e a m movement t h a n o c e a n - t y p e (P. < 0.05, F i g . 7 ) . A l t h o u g h o c e a n - t y p e c h i n o o k s showed no s i g n i f i c a n t c h a n g e i n t h e i r d e g r e e o f d o w n s t r e a m movement a t 12 months f r o m t h a t a t 9 months (P > 0 . 0 5 ) , s t r e a m - t y p e c h i n o o k s s h i f t e d f r o m " h o l d i n g " b e h a v i o u r a t 6 a n d 9 months t o p r o n o u n c e d d o w n s t r e a m movement a t 58 F i g u r e 7. N e t movement s c o r e s f o r s t r e a m - a n d o c e a n - t y p e j u v e n i l e c h i n o o k s a l m o n i n c u r r e n t r e s p o n s e t e s t s . V a l u e s a r e means ( + S E ) , N=4 p o p u l a t i o n s p e r l i f e h i s t o r y t y p e a t e a c h age e x c e p t f o r o c e a n - t y p e a t 6, 9, a n d 12 months were N=2. E=emergence, 1-6, 9, a n d 12=month o f age a t t e s t i n g . O OCEAN-TYPE: DIURNAL • OCEAN-TYPE: NOCTURNAL • STREAM-TYPE: DIURNAL • STREAM-TYPE: NOCTURNAL 3 4 AGE (months) UPSTREAM } DOWNSTREAM 60 12 months (P < 0.05) . Under s i m u l a t e d d i u r n a l c o n d i t i o n s , no d i f f e r e n c e s were a p p a r e n t b e t w e e n s t r e a m - a nd o c e a n - t y p e c h i n o o k s o v e r a l l a g e s c o m b i n e d , ( F i g . 7, P > 0.1, d f = 1 , 6 ) , b u t p o p u l a t i o n s d i f f e r e d s i g n i f i c a n t l y w i t h i n l i f e h i s t o r y t y p e (P < 0.0001, d f = 6 , 4 1 2 , T a b l e 1 2 ) . Age v a r i a t i o n i n d i u r n a l movement s c o r e s was a l s o s i g n i f i c a n t (P < 0.0001, d f = 7 , 3 6 ) . As f o r n o c t u r n a l movement, c h a n g e s i n d i u r n a l movement w i t h age i n t e r a c t e d w i t h l i f e h i s t o r y t y p e ( a g e X l i f e h i s t o r y P < 0.0.001, d f = 7 , 3 6 ) . S t r e a m -t y p e c h i n o o k s " h e l d p o s i t i o n " u n t i l 3 m o n t h s , t h e n showed s i g n i f i c a n t u p s t r e a m movement a t 4 ( p e a k ) , 6 a n d 9 months a f t e r w h i c h t h e r e was an a b r u p t r e d u c t i o n i n u p s t r e a m movement a t 12 months ( F i g . 7 ) . By c o n t r a s t , o c e a n - t y p e c h i n o o k s h e l d p o s i t i o n a t e m e rgence t h e n showed s i g n i f i c a n t u p s t r e a m movement a t 1 t h r o u g h 4 months w i t h peak movement u p s t r e a m a t 2 months ( F i g . 7 ) . By c o n t r a s t t o t h e a b r u p t r e d u c t i o n i n u p s t r e a m movement by s t r e a m - t y p e c h i n o o k s b e t w e e n 9 a n d 12 m o n t h s , o c e a n -t y p e c h i n o o k s showed no s u c h c h a n g e ; t h e y m a i n t a i n e d p o s i t i o n o r moved s l i g h t l y u p s t r e a m a t 6, 9 and 12 months (P > 0.05, F i g . 7 ) . B. I n t e r - , i n t r a p o p u l a t i o n , a n d t e m p o r a l v a r i a t i o n i n  a g g r e s s i v e b e h a v i o u r P r i n c i p a l c o m p o n e n t s a n a l y s i s s u m m a r i z e d 92% o f t h e t o t a l b e h a v i o u r a l v a r i a n c e i n two c o m p o n e n t s ( T a b l e 1 3 ) . The f i r s t 61 T a b l e 1 1 . Mean (SE) net movement s c o r e s d u r i n g n o c t u r n a l c u r r e n t response t e s t s f o r j u v e n i l e chinook salmon from the e i g h t study p o p u l a t i o n s . In each case N = 8 . For t - t e s t s of ; J = 6 , * P < 0 . 0 0 6 f o r t e s t s up to 6 months and P < 0 . 0 0 8 t h e r e a f t e r ( d f = 7 ) . Mean s c o r e s g r e a t e r or l e s s than 6 r e p r e s e n t s i g n i f i c a n t upstream or downstream movement r e s p e c t i v e l y . E=emergence. 1 - 6 , 9 and 1 2 i n d i c a t e age ( i n months) at t e s t i n g . NT=not t e s t e d . Stream-type Popu 1 a t ion Ocean - 1 ype Bowron S l i m E a g l e Salmon L. Qualicum Nanaimo Nanaimo H a r r i s o n R. Cr. R. R. R. 1st I . lower R. Age Mean E 1 . 3 2 * 1 . . 2 1 ' 2 . 4 8 * 3 . 1 3 * 2 . 0 5 * 1 . . 0 8 * 0 . 9 8 * 2 , . 8 1 * 1 . 8 6 ( 0 . 4 3 ) ( 0 . 5 2 ) ( 0 , , 5 2 ) ( 0 . 5 6 ) ( 0 . 4 7 ) ( 0 . 4 2 ) ( 0 . 4 4 ) to . 4 1 ) ( 0 . 1 9 ) 1 m 1 . 2 5 * 1 . 6 0 ' 2 , , 2 7 * 2 . 9 1 * 5 . 4 4 * 3 . , 5 3 " 3 . 9 2 * 3 . 4 7 * 3 . 0 0 ( 0 . 2 2 ) ( 0 . 3 2 ) ( 0 , 3 9 ) ( 0 . 5 6 ) ( 0 . 2 2 ) ( 0 , . 5 2 ) ( 0 . 2 1 ) ( 0 . 4 4 ) ( 0 . 2 1 ) 2 m 3 . . 3 3 * 1 . . 1 0 ' 4 , , 3 3 * 2 . 9 3 ' 5 . 7 6 * 3 , . 9 2 * 5 . 4 0 * 5 . 2 4 4 , 0 3 ( 0 . 2 7 ) ( 0 . 1 6 ) ( 0 , , 3 2 ) ( 0 . 4 1 ) ( 0 . 2 1 ) ( 0 . 4 2 ) ( 0 . 2 1 ) to . 3 2 ) ( 0 . 2 1 ) 3 m 4 . . 8 7 * 3 . . 7 2 * 4 , . 7 2 5 , . 4 6 5 . 8 6 5 , 6 1 * 5 . 2 8 5 , , 2 0 5 . . 0 8 ( 0 . . 2 1 ) ( 0 . . 3 0 ) ( 0 , 3 7 ) ( 0 . 2 0 ) ( 0 . 4 1 ) ( 0 . 4 5 ) ( 0 . 4 3 ) ( 0 , . 3 3 ) ( 0 . 1 4 ) 4 m 6 . 4 1 5 . . 4 7 " 5 . , 4 2 5 , . 2 7 5 . 7 0 5 . 5 6 5 . 7 1 5 , , 7 1 5 , . 6 5 ( 0 . . 2 5 ) ( 0 . . 2 0 ) ( 0 , , 2 3 ) ( 0 . 3 1 ) ( 0 . 1 9 ) ( 0 , , 2 9 ) ( 0 . 1 9 ) ( 0 . 1 5 ) ( 0 . 1 0 ) 6 m 5 . . 2 6 * 5 . . 7 8 6 . , 3 9 6 , . 0 8 NT 5 . , 6 8 NT 5 , . 6 7 5 . , 5 2 ( 0 . . 1 4 ) ( 0 . . 4 1 ) ( 0 . , 5 4 ) ( 0 . 5 4 ) ( 0 , , 2 0 ) ( 0 , . 1 8 ) ( 0 . 1 3 ) 9 m 5 . . 8 7 6 . . 0 8 5 . 9 0 6 , . 0 6 NT 5 . 7 4 NT 5 , , 6 8 * 5 , , 7 8 ( 0 . 4 0 ) ( 0 . 4 1 ) ( 0 . 5 4 ) ( 0 , . 5 4 ) ( 0 . , 2 8 ) ( 0 , . 1 8 ) ( 0 , . 1 7 ) 1 2 m 3 . 0 1 * 2 . . 5 1 * 3 . 1 7 * 3 , , 7 1 * NT 5 . 2 9 NT 5 , . 0 1 4 , , 0 0 ( 0 . . 4 0 ) ( 0 . 5 1 ) ( 0 . 2 0 ) ( 0 , . 4 0 ) ( 0 . 4 0 ) ( 0 , , 2 6 ) ( 0 , , 2 0 ) Mean 3 . ( 0 . 7 6 2 5 ) 3 . ( 0 . 2 7 , 2 7 ) 4 . ( 0 . , 2 0 , 2 3 ) 4 . ( 0 , . 4 5 . 2 2 ) 4 ( 0 . 9 6 . 2 6 ) 3 . ( 0 . , 8 8 3 1 ) 4 ( 0 . 7 3 . 2 2 ) 4 . ( 0 , . 7 0 , 1 9 ) 4 , ( 0 , , 2 2 , 0 9 ) 62 Table 1 2 . Mean (SE) net movement scores during d iurnal current response tests for juveni le chinook salmon from the eight study populations. A l l N=8. For t - tes t s of p=6 . *P<0.006 for tests up to 4 months and *P<0.008 thereafter ( d f = 7 ) . Mean scores greater or less than 6 represent s ign i f i cant upstream or downstream movement re spec t ive ly . E=emergence. 1-6, 9 and 12 indicate age ( in months) at t e s t ing . NT=not tested. Stream-type Popu'l at ion Ocean-type Bowron Slim Eagle Salmon L . Qualicum Nanaimo Nanaimo Harrison R. Cr . R. R. R. 1st L . lower R. Age Mean E •4. . 75 5 . 4 8 5. . 59 5 . 5 7 ' 5 . 8 6 5 . 6 3 5 . 6 3 6, , 10 5 . 57 ( 0 . 6 8 ) ( 0 . . 5 1 ) ( 0 . . 2 7 ) ( 0 . . 1 2 ) ( 0 . 2 9 ) ( 0 . 2 2 ) ( 0 . 1 7 ) ( 0 . . 1 7 ) ( 0 . 14) 1 m 5, . 60 4 . , 38 5. . 99 5. . 78 7 . s g - 5 . 9 0 7 . 9 7 - 6 . . 7 2 6 . 25 ( 0 . 6 6 ) ( 0 . . 5 1 ) ( 0 . 27 ) ( 0 . 3 7 ) i o . 3 5 ) ( 0 . 4 9 ) ( 0 . 3 3 ) ( 0 . 2 7 ) ( 0 . 21 ) 2 m 7 . . 5 3 # 3. . 5 7 ' 6 . . 14 4 . 9 6 7 .SO- 7 . 2 9 * 7 . 4 8 * 6. . 44 6 . 40 ( 0 . . 4 4 ) ( 0 . . 5 2 ) ( 0 . . 3 6 ) ( 0 . 4 5 ) I O . 3 3 ) ( 0 . 3 6 ) ( 0 . 3 5 ) ( 0 . . 3 6 ) ( 0 . 2 2 ) 3 m 7 . , 7 2 * 6 . . 5 1 7 . . 33 5. . 7 1 7 . 0 6 7 . 0 1 7 . 4 7 6 . . 82 6 . 95 ( 0 . , 5 1 ) ( 0 . . 3 0 ) ( 0 . . 6 3 ) ( 0 . . 44 ) ( 0 . 4 0 ) ( 0 , . 3 4 ) ( 0 . 34.) ( 0 . 44 ) ( 0 . 16) 4 m 9 . 6 8 * 6 . . 40 7. . 3 2 * 6 . . 6 0 * 7 . SO- 6 . 37 6 . 2 4 6 . 33 7 . 08 ( 0 . 3 9 ) ( 0 . 2 0 ) ( 0 . 6 0 ) ( 0 . . 2 0 ) fO. 3 3 ) ( 0 , . 3 2 ) ( 0 . 2 7 ) ( 0 . 19) ( 0 . 18) 6 m 7 . . 8 4 * 7 , . 0 1 . 7 . . 9 2 * 6 . . 9 7 * NT 7 . 0 1 NT 6 . 80 7 . 10 ( 0 . . 6 2 ) ( 0 , . 3 6 ) ( 0 . . 4 5 ) ( 0 , , 2 6 ) ( 0 . 3 4 ) ( 0 . 31 ) ( 0 . 2 0 ) 9 m 8 . . 5 1 * 7 . . 7 2 * 5. . 9 2 6 . . 4 0 * NT 6 . 1 1 NT 5. 72 6 . 73 ( 0 . . 7 9 ) ( 0 . 3 5 ) ( 0 . . 16) ( 0 . , 6 3 ) ( 0 , . 3 7 ) ( 0 . 3 2 ) ( 0 . 2 4 ) 12 m 5. . 2 6 6 . . 0 5 5 . .96 5. . 9 9 NT 6 . 0 4 NT 5. 87 5 . 89 ( 0 . 5 2 ) ( 0 . . 5 7 ) ( 0 . . 2 0 ) ( 0 . , 2 1 ) ( 0 , . 2 3 ) ( 0 . 2 2 ) ( 0 . 17) Mean 6 . 99 5 . 88 6 . . 48 6 . . 0 0 7 . 1 6 7 , . 0 0 6 . 3 7 6 . 24 6 . 46 ( 0 . 2 7 ) ( 0 . 2 2 ) ( 0 . . 16) ( 0 . , 15 ) ( 0 . 1 9 ) . ( 0 . . 2 0 ) ( 0 . 1 5 ) ( 0 . , 1 4 ) ( 0 I . 0 7 63 component a c c o u n t e d f o r 77% o f t h e v a r i a n c e a n d was d o m i n a t e d by "wigwag" d i s p l a y s , b u t most b e h a v i o u r s l o a d e d p o s i t i v e l y on t h i s c omponent ( T a b l e 1 3 ) . The s e c o n d c o m p o n e n t , w h i c h a c c o u n t e d f o r 15% o f t h e t o t a l v a r i a n c e , was d o m i n a t e d by " l a t e r a l d i s p l a y " , b u t , " n i p " a l s o l o a d e d h i g h l y ( T a b l e 1 3 ) . A l l s u b s e q u e n t c o m p o n e n t s a c c o u n t e d f o r l e s s t h a n 5% o f t h e t o t a l v a r i a n c e . A n a l y s i s o f v a r i a n c e o f mean PC 1 s c o r e s s u g g e s t e d t h a t o v e r a l l a g e s c o m b i n e d , t h e S l i m C r e e k , s t r e a m - t y p e j u v e n i l e s a n d t h e 1 s t L a k e Nanaimo ( o c e a n - t y p e ) c h i n o o k , w h i c h r e s i d e i n f r e s h w a t e r f o r a b o u t 2 months b e f o r e s e a w a r d m i g r a t i o n , were s i g n i f i c a n t l y more a g g r e s s i v e t h a n t h e l o w e r Nanaimo o c e a n - t y p e j u v e n i l e s w h i c h e m i g r a t e t o t h e e s t u a r y s o o n a f t e r e m ergence ( p o p u l a t i o n P < 0.0001, d f = 2 , 2 4 , F i g . 8 a ) . S l i m C r e e k s a l m o n were t h e most a g g r e s s i v e s a l m o n (P < 0.05) o v e r a l l a g e s c o m b i n e d . J u v e n i l e c h i n o o k f r o m a l l t h r e e p o p u l a t i o n s were most a g g r e s s i v e a t e m e r g e n c e , 1, a n d 2 months w i t h s i g n i f i c a n t d e c l i n e s a t o l d e r a g e s (age P < 0.0001, d f = 4 , 2 4 , F i g . 8 a ) . C h a n g e s i n a g g r e s s i v e b e h a v i o u r w i t h t i m e a l s o d i f f e r e d s i g n i f i c a n t l y among t h e t h r e e p o p u l a t i o n s ( p o p u l a t i o n x age P < 0.001, d f = 5 , 2 4 ) . A g g r e s s i v e b e h a v i o u r i n t e n s i t y i n c r e a s e d r e l a t i v e l y s t e e p l y i n t h e 1 s t L a k e Nanaimo j u v e n i l e s w i t h a peak a t 2 m onths f o l l o w e d by a s h a r p d e c l i n e a t 3 months (P < 0.05) a n d a f u r t h e r d e c l i n e a t 6 months ( F i g . 8 a ) . The e a r l i e s t s m o l t i n g l o w e r Nanaimo f i s h , h o w e v e r , had a more g r a d u a l r i s e i n a g g r e s s i v e b e h a v i o u r w i t h a peak a t 1 month f o l l o w e d by d e c l i n e s 64 T a b l e 13. B e h a v i o u r c o e f f i c i e n t s f r o m p r i n c i p a l c o m p o n e n t s a n a l y s i s o f s t r e a m t a n k b e h a v i o u r a l i n t e r a c t i o n s among j u v e n i l e c h i n o o k s a l m o n . C o e f f i c i e n t f r o m PCA B e h a v i o u r Component 1 Component 2 A p p r o a c h 0.075 0.247 L a t e r a l d i s p l a y -0.056 0.859 Wigwag 0.985 -0.034 C h a r g e 0.089 0.250 N i p 0. 109 0.369 C h a s e 0.021 0.043 C u m u l a t i v e % t o t a l v a r i a n c e 77.2 92.3 65 Figure 8. Mean (±SE) aggression scores f o r j u v e n i l e chinook. salmon f o r Nanaimo R i v e r and Slim Creek populations at s e v e r a l ages. 8 a = p r i n c i p a l component a x i s 1, 8b = p r i n c i p a l component a x i s 2. N=3 groups of 10 f r y per p o p u l a t i o n at each age. 1st Lake Nanaimo (•), lower Nanaimo ( A ) , Slim Creek ( x). COMPONENT AXIS 1 (77% TV, WIGWAGS) -» — N) N> o cn o cn o o o o o o I 1 1 1 I _ J 00 Q COMPONENT AXIS 2 (15% TV, LATERAL DISPLAYS) M *>• O CO O o o o o o o I 1 1 1 I I 99 67 a t 2 a n d 3 m o n t h s . No d a t a were c o l l e c t e d f r o m t h e S l i m C r e e k f i s h a t 1 m o n t h , b u t t h e s e f i s h were l e s s e x t r e m e i n t h e i r c h a n g e s i n a g g r e s s i v e b e h a v i o u r w i t h t i m e a n d m a i n t a i n e d s i g n i f i c a n t l y h i g h e r l e v e l s o f a g g r e s s i o n a t 3 a n d 6 months (P < 0. 05, F i g . 8a) t h a n t h e two p o p u l a t i o n s o f Nanaimo R i v e r , o c e a n -t y p e s a l m o n . A l o n g t h e s e c o n d component a x i s , t h e 1 s t L a k e Nanaimo c h i n o o k a n d t h e s t r e a m - t y p e s a l m o n f r o m S l i m C r e e k a g a i n were more a g g r e s s i v e t h a n t h e l o w e r Nanaimo f i s h a t e m e r g e n c e , b u t a t 1, 2, and 3 months 1 s t L a k e s a l m o n were most a g g r e s s i v e ( F i g . 8 b, p o p u l a t i o n P < 0 . 0 1 ) . As was t h e c a s e f o r a g g r e s s i v e b e h a v i o u r a l o n g PC 1, c h i n o o k f r o m a l l t h r e e p o p u l a t i o n s i n c r e a s e d i n a g g r e s s i v n e s s f r o m emergence t o 3 months (age P < 0.0001) b u t w i t h a d i s t i n c t d e c l i n e by 6 months (P < 0 . 0 5 ) . S l i m C r e e k j u v e n i l e s a g a i n were t h e l e a s t e x t r e m e i n t h e i r c h a n g e s i n a g g r e s s i v e n e s s w i t h t i m e . A g g r e s s i v e b e h a v i o u r i n t h e s e s t r e a m - t y p e f i s h d e c l i n e d l e s s d r a m a t i c a l l y b e t w e e n 3 a n d 6 months (P > 0.05) and t h e y w e re more a g g r e s s i v e t h a n t h e 1 s t L a k e Nanaimo R i v e r c h i n o o k by 6 months ( p o p u l a t i o n X age P < 0 . 0 0 1 ) . C. V a r i a t i o n i n g r o w t h r a t e S p e c i f i c g r o w t h r a t e (SGR) d e c l i n e d w i t h i n c r e a s i n g age o f j u v e n i l e s a l m o n ( F i g . 9 ) . No s i g n i f i c a n t d i f f e r e n c e was a p p a r e n t i n t h e s l o p e s f o r s t r e a m - a nd o c e a n - t y p e r e g r e s s i o n s 68 (Table 14, P > 0.1) and the pooled r e g r e s s i o n slope was s i g n i f i c a n t l y l e s s than zero (P < 0.0001). There were no s i g n i f i c a n t d i f f e r e n c e s among p o p u l a t i o n s w i t h i n l i f e h i s t o r y type i n a d j u s t e d SGR (P > 0.1). Ocean-type chinook, however, grew at a g r e a t e r r a t e than d i d stream-type f i s h (P < 0.01, Table 14). 69 F i g u r e 9. S p e c i f i c growth r a t e f o r stream- and ocean-type chinook salmon from emergence to 12 months of age. Each p o i n t i s the c a l c u l a t e d SGR f o r a s i n g l e p o p u l a t i o n at each age. GROWTH RATE: LAB-REARED CHINOOK 4 AGE (months) 10 o 12 71 T a b l e 14. C o v a r i a n c e a n a l y s i s summary of s p e c i f i c g r o w t h r a t e d a t a f o r s t r e a m - a n d o c e a n - t y p e c h i n o o k s a l m o n . Means (SE) a r e v a l u e s a d j u s t e d t o 6 months o f a g e . F o r a l l p o p u l a t i o n s N=12 e x c e p t f o r L. Q u a l i c u m R i v e r a n d Nanaimo l o w e r where N=4. A d j u s t e d s p e c i f i c P o p u l a t i o n g r o w t h r a t e (% bw/day) S t r e a m - t y p e Bowron R i v e r 1.12 ( 0 . 1 2 ) S l i m C r e e k 1.03 ( 0 . 1 3 ) E a g l e R i v e r 0.83 ( 0 . 1 4 ) Salmon R i v e r 1.04 ( 0 . 1 3 ) Mean 1.01 ( 0 . 0 6 ) O c e a n - t y p e L. Q u a l i c u m R i v e r 1.45 ( 0 . 2 1 ) Nanaimo l o w e r 1.26 ( 0 . 2 1 ) Nanaimo 1 s t L a k e 1.56 ( 0 . 1 2 ) H a r r i s o n R i v e r 1.26 ( 0 . 2 4 ) Mean 1.40 ( 0 . 0 7 ) C o v a r i a n c e summary by l i f e - h i s t o r y t y p e : E q u a l i t y o f s l o p e s w i t h i n : P > 0.05, d f = 6 , 6 3 E q u a l i t y o f s l o p e s b e t w e e n : P > 0.05, d f = 1 , 6 3 E q u a l i t y o f a d j u s t e d means w i t h i n : P > 0.10, df = 6,63 E q u a l i t y o f a d j u s t e d means b e t w e e n : P < 0.01, d f = 1 , 6 P o o l e d s l o p e ( S E ) : -0.17 ( 0 . 0 1 ) , P < 0.0001, r x =0.61 72 3. VARIATION IN AGGRESSIVE BEHAVIOUR AND S A L I N I T Y TOLERANCE AMONG F A M I L I E S OF J U V E N I L E CHINOOK SALMON M e t h o d s To a s s e s s f u r t h e r p h e n o t y p i c v a r i a t i o n b e t w e e n 1 s t L a k e Nanaimo a n d l o w e r Nanaimo R i v e r c h i n o o k s a l m o n , w h i c h d i f f e r i n t h e i r d u r a t i o n o f f r e s h w a t e r r e s i d e n c e , I s t u d i e d b e h a v i o u r and p h y s i o l o g y o f t h e p r o g e n y o f i n d i v i d u a l f a m i l y c r o s s e s m a i n t a i n e d s e p a r a t e l y u n d e r i d e n t i c a l e n v i r o n m e n t a l c o n d i t i o n s . By m a k i n g c r o s s e s w i t h p a r e n t s o f known f r e s h w a t e r l i f e h i s t o r y I h o p e d t o : (1) o b t a i n a b e t t e r u n d e r s t a n d i n g o f how c l o s e l y l i n k e d p h e n o t y p i c v a r i a t i o n i n b e h a v i o u r a n d p h y s i o l o g y a r e w i t h l i f e h i s t o r y v a r i a t i o n , a n d (2) compare v a r i a t i o n among f a m i l i e s w i t h i n p o p u l a t i o n s w i t h v a r i a t i o n b e t w e e n p o p u l a t i o n s . E x p e r i m e n t a l c r o s s e s J u v e n i l e s were p r o g e n y f r o m s i n g l e m a l e X f e m a l e c r o s s e s made f r o m t h e " l o w e r " ( m i g r a t e t o e s t u a r y a s f r y ) a n d " 1 s t L a k e " ( m i g r a t e t o e s t u a r y a t 2-3 m o n t h s ) s p a w n i n g p o p u l a t i o n s o f t h e Nanaimo R i v e r ( F i g 6 ) . M a t u r e a d u l t s were c o l l e c t e d a t t h e o u t l e t o f 1 s t L a k e o r i n t h e l o w e r s p a w n i n g a r e a by s t a f f f r o m t h e Nanaimo R i v e r Community Salmon H a t c h e r y d u r i n g O c t o b e r 1987. E i g h t f u l l - s i b f a m i l y m a t i n g s were c o m p l e t e d ; 3 f a m i l i e s f r o m 1 s t L a k e p o p u l a t i o n a n d 5 f r o m t h e l o w e r N a naimo. Z y g o t e s ( a b o u t 500-700 p e r c r o s s ) w e re d i s i n f e c t e d w i t h O v a d i n e and t h e n 73 p l a c e d , by f a m i l y , i n a d j a c e n t s e c t i o n s o f a s i n g l e i n c u b a t i o n t r a y (11 -12° C) a t t h e Nanaimo H a t c h e r y u n t i l t h e " e y e d " s t a g e ( a b o u t 1 m o n t h ) . A t t h e e y e d s t a g e t h e embryos were t r a n s p o r t e d o t o UBC t o c o m p l e t e i n c u b a t i o n a t 6 C. The f r e s h w a t e r l i f e h i s t o r y o f t h e p a r e n t s i n t h e c r o s s e s was a s s e s s e d f r o m 5 s c a l e s s a m p l e d f r o m b o t h s i d e s o f e a c h p a r e n t . S c a l e s were removed f r o m an a r e a b e t w e e n t h e p o s t e r i o r m a r g i n o f t h e d o r s a l f i n a n d t h e l a t e r a l l i n e a n d s t a n d a r d l e n g t h was d e t e r m i n e d f o r e a c h p a r e n t . S c a l e i m p r e s s i o n s were made f o l l o w i n g t h e m e t h o d o l o g y o f C l u t t e r a n d W h i t e s e l ( 1 9 5 6 ) . P h o t o g r a p h i c p r i n t s were made o f e a c h s c a l e i m p r e s s i o n a t 34X m a g n i f i c a t i o n u n d e r a 3M m i c r o f i c h e r e a d e r - p r i n t e r . F r e s h w a t e r c i r c u l i c o u n t s were made f r o m t h e p r o j e c t e d s c a l e i m p r e s s i o n s ( 100X) w i t h t h e a s s i s t a n c e o f a t e c h n i c i a n f r o m t h e D e p a r t m e n t o f F i s h e r i e s a n d Oce a n s S c a l e M o r p h o l o g y L a b o r a t o r y ( 555 West H a s t i n g s S t r e e t , V a n c o u v e r , B C ) . F r e s h w a t e r c i r c u l i were i d e n t i f i e d a s t h e r e l a t i v e l y t h i n , t i g h t l y - s p a c e d c i r c u l i n e a r t h e s c a l e f o c u s ( F i g . 1 0 ) . E s t u a r i n e a n d / o r o c e a n c i r c u l i w ere i d e n t i f i e d by l o o k i n g f o r an a b r u p t i n c r e a s e i n t h e w i d t h a n d / o r s p a c i n g o f c i r c u l i ( F i g . 1 0 ) . A measure o f d u r a t i o n o f f r e s h w a t e r r e s i d e n c e o f t h e p a r e n t s was o b t a i n e d by c o u n t i n g t h e number o f t i g h t l y - s p a c e d , t h i n f r e s h w a t e r c i r c u l i ; f i s h w i t h more f r e s h w a t e r c i r c u l i were assumed t o have s p e n t more t i m e i n f r e s h w a t e r . I n a d d i t i o n t o t h e Nanaimo R i v e r c r o s s e s , p r o g e n y r e s u l t i n g 74 F i g u r e 1 0 . Photomicrograph of a d u l t chinook salmon s c a l e i l l u s t r a t i n g key f e a t u r e s used to determine j u v e n i l e l i f e h i s t o r y p a t t e r n . SF=scale focus from where freshwater c i r c u l i begin, EG=beginning of e s t u a r i n e growth, MG=beginning of marine growth. 75 76 f r o m m a t i n g s o f 15 f e m a l e and 10 m a l e S q u a m i s h R i v e r ( F i g . 1) c h i n o o k s a l m o n were o b t a i n e d i n l a t e S e p t e m b e r 1987. The o z y g o t e s f r o m t h e s e c r o s s e s were m i x e d and i n c u b a t e d a t 11 C f o r 1 month a t t h e S q u a m i s h R i v e r H a t c h e r y a n d t h e n t r a n s p o r t e d t o o UBC t o c o m p l e t e i n c u b a t i o n a t 6 C. S q u a m i s h R i v e r c h i n o o k a r e a c o a s t a l s p a w n i n g p o p u l a t i o n w h i c h a r e p r e d o m i n a t e l y s t r e a m - t y p e ( u n p u b l . d a t a , C h a p t e r 2 ) . Upon e m e r g e n c e , e a c h o f t h e e i g h t f a m i l i e s o f Nanaimo c h i n o o k a n d f r y f r o m t h e S q u a m i s h R i v e r ( h e r e a f t e r r e f e r r e d t o a s t h e e x p e r i m e n t a l g r o u p s ) were a s s i g n e d r a n d o m l y t o one o f n i n e , 94 L r e a r i n g t r o u g h s , where t h e y were m a i n t a i n e d u n d e r c o n d i t i o n s o f w a t e r f l o w , w a t e r t e m p e r a t u r e , d i e t , a nd a n a t u r a l p h o t o p e r i o d r e g i m e a s d e s c r i b e d e a r l i e r ( 1 . 1 ) . S i z e - a t - e m e r g e n c e ( s t a n d a r d l e n g t h , f o r k l e n g t h , a n d wet w e i g h t ) were d e t e r m i n e d f o r e a c h e x p e r i m e n t a l g r o u p and g r o w t h was m o n i t o r e d a t m o n t h l y i n t e r v a l s a s d e s c r i b e d p r e v i o u s l y ( 1 . 1 ) . A. V a r i a t i o n i n a g g r e s s i v e b e h a v i o u r S t u d i e s o f a g g r e s s i v e b e h a v i o u r o f j u v e n i l e c h i n o o k f r o m t h e n i n e e x p e r i m e n t a l g r o u p s t o o k p l a c e i n t h r e e s t r e a m t a n k s . E a c h s t r e a m t a n k (1.4 X 0.9 X 0.30 m) was d i v i d e d i n t o two p a r a l l e l s t r e a m c h a n n e l s (1.0 X 0.35 X 0.30 m) w h i c h were s e p a r a t e d f r o m e a c h o t h e r by a c e n t r a l c o m p a r t m e n t (1.0 X 0.25 X 0.30 m). One s i d e o f e a c h s t r e a m c h a n n e l was f o r m e d by 0.5 cm t h i c k P l e x i g l a s s f o r v i e w i n g . E a c h s t r e a m c h a n n e l was i s o l a t e d f r o m t h e s u r r o u n d i n g a r e a by s t a i n l e s s s t e e l w i r e mesh b a r r i e r s 77 (0.30 cm mesh a t emergence a n d 1 month, 0.65 cm mesh a t 2 a n d 3 months o f age) a t t h e u p s t r e a m and d o w n s t r e a m e n d s . E n v i r o n m e n t a l c o n d i t i o n s w i t h i n e a c h s t r e a m c h a n n e l (n=6, 2 c h a n n e l s f o r e a c h o f t h e t h r e e s t r e a m t a n k s ) were a s d e s c r i b e d o e a r l i e r ; g r a v e l a n d s t o n e s u b s t r a t e , 10 C, n a t u r a l p h o t o p e r i o d w i t h 0.5 h "dawn" and " d u s k " p e r i o d s d a i l y ) . The o b s e r v e r was v i s u a l l y i s o l a t e d f r o m e a c h s t r e a m c h a n n e l by b l a c k p l a s t i c s h e e t i n g w i t h o b s e r v a t i o n h o l e s . To encompass t h e v a r i o u s a g e s - a t - m i g r a t i o n f o r Nanaimo R i v e r c h i n o o k , s a l m o n b e h a v i o u r was o b s e r v e d a t e m e r g e n c e a n d a t 1, 2, a n d 3 months o f a g e . A t e a c h a g e , I o b t a i n e d two o r t h r e e s a m p l e s o f t e n j u v e n i l e s f r o m e a c h e x p e r i m e n t a l g r o u p a n d a s s i g n e d them r a n d o m l y t o a s e p a r a t e s t r e a m c h a n n e l 48 h b e f o r e t h e s t a r t o f o b s e r v a t i o n s . F o r 5 m i n , t w i c e d a i l y f o r 5 c o n s e c u t i v e d a y s , I r e c o r d e d t h e f r e q u e n c y a n d d u r a t i o n o f " n u l l " , " a p p r o a c h " , " n i p " , " c h a r g e " , a n d " d i s p l a y " b e h a v i o u r s ( b o t h " l a t e r a l " a n d "wigwag" d i s p l a y s , s e e T a b l e 1 f o r d e f i n i t i o n s ) a s w e l l a s two n o n - a g g r e s s i v e b e h a v i o u r s : " f o r a g e " a n d "yawn". " F o r a g e " was d e f i n e d a s any swimming movement c o v e r i n g a t l e a s t 2 b o d y l e n g t h s f o l l o w e d by a t t e m p t e d i n g e s t i o n , a n d "yawn" c o n s i s t e d o f an e x a g g e r a t e d o p e n i n g o f t h e mouth a c c o m p a n i e d by p r o n o u n c e d g i l l f l a r i n g and t e r m i n a t e d w i t h r a p i d c l o s i n g o f t h e mouth. J u v e n i l e s were f e d t h r o u g h t u b e s l o c a t e d a t t h e u p s t r e a m e n d s o f e a c h s t r e a m c h a n n e l a f t e r e a c h o b s e r v a t i o n p e r i o d , a n d 78 a t m i d - d a y , a t a r a t e o f 5-6% bw/d. L i v e A r t e m i a n a u p l i i were f e d t o n e w l y - e m e r g e d a n d 1 month o l d c h i n o o k , t h e r e a f t e r f r o z e n C h i r o n o m u s l a r v a e were u s e d a s f o o d . B. V a r i a t i o n i n s a l i n i t y t o l e r a n c e V a r i a t i o n among e x p e r i m e n t a l g r o u p s o f j u v e n i l e c h i n o o k i n a b i l i t y t o t o l e r a t e h y p e r s a l i n e w a t e r was i n v e s t i g a t e d u s i n g " s e a w a t e r c h a l l e n g e " t e s t s ( C l a r k e a n d B l a c k b u r n 1977, B l a c k b u r n and C l a r k e 1 9 8 7 ) . When f r e s h w a t e r a c c l i m a t e d f i s h e s a r e p l a c e d i n h y p e r s a l i n e w a t e r , o s m o t i c s t r e s s o c c u r s a n d i s r e f l e c t e d i n c h a n g e s i n b l o o d c h e m i s t r y ( p l a s m a s o d i u m l e v e l s , o s m o l a l i t y ) , m o i s t u r e c o n t e n t a n d s u r v i v a l , a l l o f w h i c h a r e i n t e r c o r r e l a t e d ( B l a c k b u r n a n d C l a r k e 1 9 8 7 ) . W e i g h t l o s s ( d e h y d r a t i o n ) a n d m o r t a l i t y , due t o h y p e r s a l i n e t r a n s f e r , were r e c o r d e d a t 2 0 % o s e a w a t e r , w h i c h i s r e p r e s e n t a t i v e o f t h e Nanaimo R i v e r e s t u a r y ( H e a l e y 1980) and a t 3 0 % o w h i c h i s r e p r e s e n t a t i v e o f n e a r s h o r e m a r i n e s a l i n i t i e s a n d i s t h e most common s a l i n i t y u s e d i n s e a w a t e r c h a l l e n g e t e s t s . F i l t e r e d s e a w a t e r f r o m B u r r a r d I n l e t was s t a n d a r d i z e d t o 3 0 % o by a d d i t i o n o f s a l t a n d 2 0 % o s e a w a t e r was p r e p a r e d by d i l u t i o n w i t h d e c h l o r i n a t e d t a p w a t e r . S a l i n i t i e s were d e t e r m i n e d w i t h t h e a i d o f a h y d r o m e t e r . " S t a t i c " 24 h s e a w a t e r c h a l l e n g e t e s t s ( B l a c k b u r n a n d C l a r k e 1987) were r u n i n . f i v e , 75 L p l a s t i c g a r b a g e p a i l s i n a c o n t r o l l e d e n v i r o n m e n t chamber (10 C ) . F o r e a c h t e s t , t h r e e p a i l s were r a n d o m l y a s s i g n e d a s e x p e r i m e n t a l ( c o n t a i n i n g s a l i n e 79 w a t e r ) a n d t h e o t h e r two a s f r e s h w a t e r c o n t r o l s . T e s t s w e re r u n on t h e p r o g e n y f r o m e a c h e x p e r i m e n t a l g r o u p a t e m e r g e n c e , a n d a t 1, 2, a n d 3 months o f a g e . T w e n t y - f o u r h b e f o r e a t e s t , 50 f i s h were i s o l a t e d a n d d e p r i v e d o f f o o d f o r 24 h, t h e n s e p a r a t e d i n t o f i v e g r o u p s o f 10, b l o t t e d on m o i s t p a p e r t o w e l , a n d w e i g h e d i n d i v i d u a l l y t o t h e n e a r e s t 0.001 g. E a c h g r o u p o f 10 was t h e n r e t u r n e d t o f r e s h w a t e r t o r e c o v e r f r o m h a n d l i n g . A f t e r 1 h, e a c h g r o u p o f f i s h was p l a c e d i n one o f t h e f i v e p a i l s a n d l e f t f o r 24 h. A i r b u b b l e r s i n e a c h p a i l p r o v i d e d a e r a t i o n . A f t e r 24 h, t h e s u r v i v o r s i n e a c h p a i l were e n u m e r a t e d , c o l l e c t e d , a n d i n d i v i d u a l l y w e i g h e d t o t h e n e a r e s t 0.001 g and p r e s e r v e d i n 10% b u f f e r e d f o r m a l i n . S u b s e q u e n t l y , p e r c e n t a g e w e i g h t l o s s f o r e a c h g r o u p was a d j u s t e d by s u b t r a c t i o n o f t h e p e r c e n t a g e w e i g h t l o s s o f t h e f r e s h w a t e r c o n t r o l s . C. S t a t i s t i c a l a n a l y s i s D a t a on t h e a g g r e s s i v e b e h a v i o u r o f j u v e n i l e c h i n o o k were s u m m a r i z e d i n t o p r i n c i p a l component s c o r e s f o r e a c h o b s e r v a t i o n . S u b s e q u e n t l y , a mean PC s c o r e was c a l c u l a t e d o v e r a l l r e p e a t e d m e a s u r e s ( o b s e r v a t i o n p e r i o d s a n d o b s e r v a t i o n d a y s ) . The mean PC s c o r e s w e re a n a l y s e d by f a c t o r i a l , n e s t e d a n a l y s i s o f v a r i a n c e ; age a n d p o p u l a t i o n were t h e m a i n e f f e c t s a n d f a m i l y was n e s t e d w i t h i n p o p u l a t i o n . D a t a on p e r c e n t a g e s u r v i v a l a n d w e i g h t l o s s i n s e a w a t e r were a r c s i n e s q u a r e - r o o t t r a n s f o r m e d 80 p r i o r t o a n a l y s i s a n d s u b j e c t e d t o f a c t o r i a l , n e s t e d a n a l y s i s o f c o v a r i a n c e w i t h l n s t a n d a r d l e n g t h a s t h e c o v a r i a t e . I n a l l t e s t s , h o m o g e n e i t y o f v a r i a n c e t e s t s were r u n u s i n g B a r t l e t t ' s t e s t a n d a p o s t e r i o r i means t e s t s f o l l o w e d T u k e y ' s p r o c e d u r e . S i n c e t h e f a m i l i e s o f S q u a m i s h R i v e r s a l m o n were n o t k e p t s e p a r a t e a f t e r f e r t i l i z a t i o n , t h e i r d a t a were n o t c o m p a r e d s t a t i s t i c a l l y w i t h t h o s e d a t a o f Nanaimo R i v e r f a m i l i e s . R e s u l t s A. A d u l t f r e s h w a t e r r e a r i n g l i f e h i s t o r y D u r a t i o n o f f r e s h w a t e r r e s i d e n c e among t h e a d u l t c h i n o o k u s e d f o r e x p e r i m e n t a l c r o s s e s ( a s i n f e r r e d f r o m f r e s h w a t e r c i r c u l i c o u n t s ) r a n g e d f r o m 7 t o 21 c i r c u l i ( T a b l e 1 5 ) . F i r s t L a k e f a m i l y 3 had p a r e n t s w i t h t h e h i g h e s t mean f r e s h w a t e r c i r c u l i c o u n t ( 1 7 . 5 ) ; t h e f e m a l e h a d a f r e s h w a t e r a n n u l u s a n d 21 c i r c u l i , t h e m a l e had 14 c i r c u l i . L o w e r Nanaimo f a m i l y 5 had t h e f e w e s t f r e s h w a t e r c i r c u l i (mean=7.5). S q u a m i s h R i v e r a d u l t s ' f r e s h w a t e r c i r c u l i c o u n t s r a n g e d b e t w e e n 10 a n d 21 ( T a b l e 1 5 ) . A d u l t s , e s p e c i a l l y f e m a l e s , t e n d e d t o be l a r g e r i n t h e l o w e r Nanaimo p o p u l a t i o n a n d t e n d e d t o p r o d u c e l a r g e r f r y a t e m e r g e n c e (0.46+0.07 v s 0.39+0.05 g, P>0.05, d f = 1 , 6 ) , b u t i n t e r f a m i l y d i f f e r e n c e s were more n o t a b l e ( P<0.0001, d f = 6 , 2 3 2 , F i g . 1 1 ) . 81 Table 15. Parental standard length (cm), number of freshwater c i r c u l i (FWC) and mean (SE, N=30) wet weights (g) of newly emerged fry from the Nanaimo and Squamish r i v e r s . Among fami l ies within the Nanaimo River populations, those mean fry weights not annotated by the same le t ter are s i g n i f i c a n t l y d i f f e r e n t (Tukey's P < 0.05). 1st Lower Squamish Lake famil ies Nanaimo famil ies River Tra i t 1 2 3 1 2 3 4 5 Female SL 75 76 74 73 75 81 82 83 62- 86 Male SL 62 77 70 72 80 84 83 63 54- 86 Female FWC 12 10 21 10 9 8 7 8 12- 20 Male FWC 8 8 14 10 10 1 1 9 7 10- 21 Mean FWC 10 9 17.5 10 9.5 9 . 5 8 7 . 5 -Fry weight 0 ,42a 0. 43a 0. 34b 0. . 37a 0 ,46b 0. . 43c 0 . 57d 0. . 50e 0. 34 (0 .02) (0. .03) (0.03) (0. .03) (0. .03) (0. .03) (0. .02) (0. .03) (0. 03) 82 Figure 11. Re lat ionship between female standard length and fry wet weight at emergence for Nanaimo River chinook salmon. 0.60H 0.55 H B 1st LAKE NANAIMO • LOWER NANAIMO • 0.50H • 0.45 H 0.40 H 0.35H • • • 0.30H I I i 1 1 1 r— 72 74 76 78 8 0 82 84 FEMALE STANDARD LENGTH (cm) 84 B. V a r i a t i o n i n a g g r e s s i v e b e h a v i o u r V a r i a t i o n i n b e h a v i o u r among t h e n i n e e x p e r i m e n t a l g r o u p s was s u m m a r i z e d i n 2 p r i n c i p a l c o m p o n e n t s ( 9 7 % o f t h e t o t a l v a r i a t i o n , T a b l e 1 6 ) . A g g r e s s i v e b e h a v i o u r s ( " l a t e r a l d i s p l a y " P C1, " a p p r o a c h " PC2) d o m i n a t e d b o t h a x e s w h i l e n o n - a g g r e s s i v e b e h a v i o u r s h a d c o n s i s t e n t l y l o w l o a d i n g s . A l o n g t h e f i r s t p r i n c i p a l c o m p o n e n t , 1 s t L a k e j u v e n i l e c h i n o o k were s t r i k i n g l y more a g g r e s s i v e t h a n c h i n o o k f r o m t h e l o w e r Nanaimo R i v e r p o p u l a t i o n ( F i g . 12a, P=0.0002, d f = 1 , 6 ) . M a r g i n a l l y s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s were a l s o e v i d e n t among f a m i l i e s w i t h i n p o p u l a t i o n s ( T a b l e 17, P=0.04, d f = 6 , 4 5 ) . Age was a l s o a s i g n i f i c a n t f a c t o r (P= 0.05, d f = 3 , l 8 ) ; j u v e n i l e c h i n o o k f r o m a l l g r o u p s r e a c h e d m a x i m a l a g g r e s s i v e n e s s a t 2 m onths w i t h a s i g n i f i c a n t d e c l i n e a t 3 months ( F i g . 1 2 a ) . No s i g n i f i c a n t i n t e r a c t i o n s were e v i d e n t among t h e m a i n f a c t o r s (P > 0.1 ) . S t r e a m - t y p e c h i n o o k f r o m t h e S q u a m i s h R i v e r h a d s i m i l a r l y h i g h a g g r e s s i o n s c o r e s t o t h o s e o f 1 s t L a k e s a l m o n a l o n g t h e f i r s t PC a x i s , b u t were more a g g r e s s i v e t h a n c h i n o o k f r o m b o t h p o p u l a t i o n s o f t h e Nanaimo R i v e r by 3 months ( F i g . 1 2 a ) . T h e r e was a s i g n i f i c a n t d i f f e r e n c e b e t w e e n t h e Nanaimo R i v e r p o p u l a t i o n s a l o n g t h e s e c o n d component a x i s ( " a p p r o a c h " , T a b l e 17, F i g . 12b, P=0.05, d f = 1 , 6 ) ; a g a i n t h e 1 s t L a k e c h i n o o k 85 T a b l e 16. B e h a v i o u r c o e f f i c i e n t s f r o m p r i n c i p a l c o m p o n e n t s a n a l y s i s o f j u v e n i l e c h i n o o k s a l m o n i n t e r a c t i o n . B e h a v i o u r C o e f f i c i e n t Component 1 f r o m PCA Component 2 A p p r o a c h 0.065 0.867 L a t e r a l d i s p l a y 0.987 -0.123 C h a r g e 0.094 0.221 N i p 0.1 06 0.425 F o r a g e -0.001 0.004 Yawn -0.002 0.055 C u m u l a t i v e % t o t a l v a r i a n c e 94.1 97.3 86 F i g u r e 12. Mean (+SE) a g g r e s s i o n s c o r e s f o r j u v e n i l e c h i n o o k s a l m o n f r o m t h e Nanaimo R i v e r f a m i l i e s a n d S q u a m i s h R i v e r o v e r 3 months o f a g e . 1 2 a = p r i n c i p a l component a x i s 1, 1 2 b = p r i n c i p a l component a x i s 2. F o r 1 s t L a k e N=7, 6, 6, 7, f o r l o w e r Nanaimo N=11, 12, 13, 15 a n d f o r S q u a m i s h N=2, 2, 2, and 3 a t e m e r g e n c e , 1, 2 a n d 3 months o f age r e s p e c t i v e l y . 12a 12b • NANAIMO RIVER: 1ST LAKE A NANAIMO RIVER: LOWER RIVER X SQUAMISH RIVER I \ i i i r E 1 2 3 AGE (months) co 88 T a b l e 17. Mean (+SE) a g g r e s s i o n s c o r e s f o r j u v e n i l e c h i n o o k f r o m t h e Nanaimo a n d S q u a m i s h r i v e r s . Component a x i s E x p e r i m e n t a l g r o u p N PC1 PC2 1 s t L a k e F a m i l y 1 9 F a m i l y 2 9 F a m i l y 3 9 Lower Nanaimo F a m i l y 1 12 F a m i l y 2 9 F a m i l y 3 11 F a m i l y 4 9 F a m i l y 5 10 S q u a m i s h R i v e r 9 73.5 (6.1 ) 10.3 (1 .5) 66. 1 ( 4 . 7 ) 8.3 (0 .5) 78.9 ( 7 . 0 ) 5.4 (1 .0) 30.3 ( 2 . 8 ) 5.6 (0 .7) 27.8 ( 3 . 0 ) 5.9 (0 .9) 42.5 (4.1 ) 5.4 (1 .0) 26.4 ( 2 . 7 ) 5.8 (0 .8) 36.2 ( 4 . 5 ) 4.9 (0 .8) 77.7 ( 7 . 5 ) 12.1 (1 .4) 89 were more a g g r e s s i v e t h a n t h e l o w e r r i v e r p o p u l a t i o n . No d i f f e r e n c e s i n a g g r e s s i v e b e h a v i o u r a l o n g t h e " a p p r o a c h " a x i s were f o u n d among f a m i l i e s n e s t e d w i t h i n p o p u l a t i o n ( T a b l e 17, P=0.1, d f = 6 , 4 5 ) . A l o n g t h i s s e c o n d a x i s , j u v e n i l e c h i n o o k t e n d e d t o be most a g g r e s s i v e a t emergence w h i l e b e i n g l e s s a g g r e s s i v e a t 1, 2, and 3 months ( F i g . 12b, age P = 0 . 0 0 6 ) . B o t h p o p u l a t i o n s a n d a l l f a m i l i e s w i t h i n p o p u l a t i o n s showed no s i g n i f i c a n t d i f f e r e n c e s i n t r e n d s i n a g g r e s s i o n w i t h t i m e ( a l l i n t e r a c t i o n s P > 0 . 1 ) . S q u a m i s h R i v e r f r y t e n d e d t o h a v e h i g h e r s c o r e s a l o n g t h e s e c o n d component a x i s t h a n t h e Nanaimo R i v e r p o p u l a t i o n s ( F i g . 1 2 b ) . C. V a r i a t i o n i n s a l i n i t y t o l e r a n c e j _ . E f f e c t s o f s i z e on s a l i n i t y t o l e r a n c e A t e m e r g e n c e , most j u v e n i l e c h i n o o k s u r v i v e d 24 h e x p o s u r e t o 20%© s e a w a t e r ; o n l y t h r e e f a m i l i e s e x p e r i e n c e d m o r t a l i t y : 1 s t L a k e f a m i l i e s 2 a n d 3 (30 a n d 3 7 % ) , a n d l o w e r Nanaimo f a m i l y 1 ( 1 7 % ) . A t o l d e r a g e s t h e r e was no m o r t a l i t y i n any e x p e r i m e n t a l g r o u p i n 20%© s e a w a t e r . A t e m e r g e n c e and u n t i l t e s t i n g a t 3 m o n t h s , p e r c e n t a g e w e i g h t l o s s a f t e r 24 h i n 2 0 % o s e a w a t e r was s t r o n g l y s i z e - d e p e n d e n t i n t h e j u v e n i l e s a l m o n ( F i g . 1 3 a ) ; s m a l l e r j u v e n i l e s , b o t h w i t h i n a n d b e t w e e n f a m i l i e s , l o s t p r o p o r t i o n a l l y more w e i g h t . S u r v i v a l a f t e r 24 h e x p o s u r e t o 90 F i g u r e 13. R e l a t i o n s h i p between body s i z e and measures of s a l i n i t y t o l e r a n c e i n j u v e n i l e chinook salmon over 3 months of age. 13a = weight l o s s in 20% oseawater as a f u n c t i o n of f i s h s i z e , 13b = percentage s u r v i v a l i n 30% oseawater as a f u n c t i o n of f i s h s i z e . 13a o 30 100 STANDARD LENGTH (mm) 13b • O • • C r • STANDARD LENGTH (mm) AGE • EMERGENCE • 1 MONTH • 2 MONTHS O 3 MONTHS 92 3 0 % o s e a w a t e r was much l o w e r t h a n f o r 2 0 % o a n d was a l s o s i z e -d e p e n d e n t ( F i g . 1 3 b ) ; a g a i n , l a r g e r f i s h were b e t t e r a b l e t o s u r v i v e . T h e r e was no s u r v i v a l i n e i g h t o f n i n e g r o u p s o f s a l m o n when e x p o s e d t o 30%o s e a w a t e r a t e m e r g e n c e , b u t s u r v i v a l was s u b s t a n t i a l i n some f a m i l i e s a t 1 month a n d r e a c h e d 100% i n l o w e r Nanaimo f a m i l i e s 4 a n d 5 a t 2 months ( F i g . 1 4 ) . W h i l e l i n e a r m o d e l s e x p l a i n e d v a r i a t i o n i n w e i g h t l o s s ( r =0.80) a n d s u r v i v a l ( r =0.73) i n t e r m s o f s i z e v a r i a t i o n , t h e r e i s some s u g g e s t i o n t h a t b o t h m e a s u r e s o f s a l i n i t y t o l e r a n c e i n c r e a s e d a b r u p t l y a t 55-65 mm ( S L ) o r 2.0-3.5 g. ( F i g . 13a,b, c_f. C l a r k e a n d S h e l b o u r n 1 9 8 5 ) . 2. V a r i a t i o n i n w e i g h t l o s s a n d s u r v i v a l From emergence t o 3 m o n t h s , t h e s m a l l e r 1 s t L a k e c h i n o o k l o s t a g r e a t e r p e r c e n t a g e o f t h e i r w e i g h t when e x p o s e d t o 2 0 % o s e a w a t e r t h a n c h i n o o k f r o m t h e l o w e r Nanaimo p o p u l a t i o n ( 4 . 5 % v s 1 . 8 % ) . When a d j u s t e d t o a common s t a n d a r d l e n g t h (53 mm), f i s h f r o m b o t h p o p u l a t i o n s l o s t a s i m i l a r p e r c e n t a g e o f w e i g h t ( 1 s t L a k e : 3.2% y_s l o w e r N a naimo: 2.3%, P=0.3, d f = 1 , 6 ) . S i g n i f i c a n t v a r i a t i o n , h o w e v e r , was a p p a r e n t among f a m i l i e s w i t h i n p o p u l a t i o n s a t a common s i z e (P=0.0002, d f = 6 , 4 9 , T a b l e 1 8 ) . A l l c h i n o o k l o s t l e s s w e i g h t w i t h i n c r e a s i n g age ( a n d i n c r e a s i n g s i z e , F i g . 1 4 ) , b u t i n t e r p r e t a t i o n o f age v a r i a t i o n i n w e i g h t l o s s i n d e p e n d e n t o f d i f f e r e n c e s i n s t a n d a r d l e n g t h was c o m p r o m i s e d by h e t e r o g e n e i t y among age g r o u p v a r i a n c e s a n d w e i g h t l o s s on SL r e g r e s s i o n s l o p e s ( b o t h P < 0 . 0 1 ) . F i g u r e 14. Changes i n percentage s u r v i v a l a f t e r exposure to 30% seawater with time i n Nanaimo and Squamish r i v e r s chinook over t h e i r f i r s t 3 months of age. Each p o i n t the mean of 3 groups of 10 f i s h per group at each age. • 1ST LAKE: FAMILY 1 • 1ST LAKE: FAMILY 2 • 1ST LAKE^ FAMILY_3 _ O LOWER NANAIMO: FAMILY 1 A LOWER NANAIMO: FAMILY 2 _! ! 1 p E 1 2 3 AGE (months) 95 T a b l e 18. P e r c e n t a g e w e i g h t l o s s a f t e r 24 h i n 20%© s e a w a t e r f o r j u v e n i l e c h i n o o k s a l m o n . V a l u e s (mean+SE) a r e a v e r a g e d o v e r 3 months a n d a r e a d j u s t e d t o an o v e r a l l s i z e o f 53 mm SL. F o r c o m p a r i s o n among f a m i l i e s w i t h i n p o p u l a t i o n s . E x p e r i m e n t a l g r o u p N P e r c e n t a g e w e i g h t l o s s 1 s t L a k e F a m i l y 1 F a m i l y 2 F a m i l y 3 1 2 12 1 2 1 .95 3.55 4.10 ( 0 . 7 2 ) ( 0 . 7 5 ) ( 0 . 8 4 ) Lower Nanaimo F a m i l y 1 F a m i l y 2 F a m i l y 3 F a m i l y 4 F a m i l y 5 1 2 1 2 1 2 1 2 1 2 3.15 1.31 1 .98 2.20 3.85 ( 1 . 0 9 ) ( 0 . 6 3 ) ( 0 . 6 3 ) ( 0 . 9 8 ) ( 1 . 1 8 ) S q u a m i s h R i v e r 12 5.50 ( 0 . 8 9 ) 96 Over t h e 3 month t e s t p e r i o d , l o w e r Nanaimo c h i n o o k h ad a h i g h e r mean s u r v i v a l r a t e a f t e r 24 h e x p o s u r e t o 30%o s e a w a t e r (34.2+1.5% v s 13.2+1.9%), b u t a f t e r a d j u s t m e n t t o a common s t a n d a r d l e n g t h (54 mm) s u r v i v a l r a t e s were s i m i l a r b e t w e e n t h e two p o p u l a t i o n s o f Nanaimo c h i n o o k ( b o t h 2 5 - 2 6 % ) . T h e r e was, h o w e v e r , s i g n i f i c a n t v a r i a t i o n among f a m i l i e s w i t h i n p o p u l a t i o n s (P = 0.0001, d f = 6 , 4 9 , T a b l e 19) a f t e r a d j u s t m e n t f o r s i z e d i f f e r e n c e s . W i t h i n t h e 1 s t L a k e p o p u l a t i o n , f a m i l y 3 h a d t h e l o w e s t o v e r a l l s u r v i v a l w h i l e f a m i l y 1 had t h e h i g h e s t ( a n d t h i r d h i g h e s t s u r v i v a l among a l l e i g h t f a m i l i e s ) . Among t h e l o w e r Nanaimo f a m i l i e s f a m i l y 4 h a d t h e h i g h e s t s u r v i v a l w h i l e f a m i l y 1 h a d t h e l o w e s t . S u r v i v a l i n c r e a s e d w i t h i n c r e a s i n g a g e , b u t h e t e r o g e n e o u s e r r o r v a r i a n c e s among t h e age c l a s s e s c o m p r o m i s e d s t a t i s t i c a l a n a l y s i s . Where v a r i a n c e s were s i m i l a r , h o w e v e r , ( i . e . e mergence a n d 3 m o n t h s ) s i z e - i n d e p e n d e n t s u r v i v a l was much h i g h e r a t t h e o l d e r a g e . B o t h p o p u l a t i o n s a n d a l l f a m i l i e s w i t h i n p o p u l a t i o n s i n c r e a s e d s u r v i v a l i n 3 0 % o s e a w a t e r w i t h i n c r e a s i n g age i n s i m i l a r f a s h i o n ( a l l i n t e r a c t i o n s P > 0.3, F i g . 1 4 ) . Salmon f r o m t h e S q u a m i s h R i v e r ( s t r e a m - t y p e ) p e r f o r m e d p o o r l y i n s a l i n e w a t e r r e l a t i v e t o b o t h p o p u l a t i o n s o f Nanaimo R i v e r o c e a n - t y p e c h i n o o k ( T a b l e s 18-19, F i g . 1 4 ) . Ov e r t h e 3 month t e s t p e r i o d , S q u a m i s h R i v e r c h i n o o k a v e r a g e d a b o u t 5.5% w e i g h t l o s s i n 20%© s e a w a t e r a n d 13% s u r v i v a l i n 3 0 % o s e a w a t e r c o m p a r e d t o a v e r a g e s of. 2.0-3.0% a n d 25% b o t h f o r 1 s t L a k e a n d 97 T a b l e 19. P e r c e n t a g e s u r v i v a l a f t e r 24 h i n 3 0 % o s e a w a t e r f o r j u v e n i l e c h i n o o k s a l m o n . V a l u e s (mean+SE) a r e a v e r a g e d o v e r 3 months and a r e a d j u s t e d t o an o v e r a l l s i z e o f 54 mm SL. E x p e r i m e n t a l g r o u p N P e r c e n t a g e s u r v i v a l 1 s t L a k e F a m i l y 1 12 37.0 ( 3 . 2 2 ) F a m i l y 2 12 26.0 ( 3 . 4 6 ) F a m i l y 3 12 22.1 ( 5 . 1 1 ) Lower Nanaimo F a m i l y 1 12 25.8 ( 5 . 1 4 ) F a m i l y 2 12 30.0 ( 2 . 9 3 ) F a m i l y 3 12 32.6 ( 2 . 9 6 ) F a m i l y 4 12 4 3 . 7 ( 5 . 9 1 ) F a m i l y 5 12 43.3 ( 4 . 6 6 ) S q u a m i s h R i v e r 12 13.1 ( 4 . 5 8 ) 98 l o w e r Nanaimo R i v e r c h i n o o k o f t h e same s i z e . P e r c e n t a g e w e i g h t l o s s i n 20%o s e a w a t e r a n d s u r v i v a l i n 3 0 % o , a s two m e a s u r e s o f s a l i n i t y t o l e r a n c e , were w e l l c o r r e l a t e d ( r = 0 . 9 2 , P < 0.01,- 7 d f ) among t h e e x p e r i m e n t a l g r o u p s o f s a l m o n . J u v e n i l e s f r o m g r o u p s t h a t l o s t t h e most w e i g h t i n 2 0 % o s e a w a t e r e x p e r i e n c e d t h e h i g h e s t m o r t a l i t y i n 3 0 % o s e a w a t e r . D. C o r r e l a t i o n s among v a r i a b l e s F r e s h w a t e r l i f e h i s t o r y o f t h e p a r e n t s o f t h e Nanaimo R i v e r f a m i l i e s a n d t h e S q u a m i s h R i v e r t e n d e d t o be r e l a t e d t o t h e b e h a v i o u r a l a n d p h y s i o l o g i c a l p e r f o r m a n c e m e a s u r e s o f t h e i r p r o g e n y ( T a b l e 2 0 ) . F r e s h w a t e r c i r c u l i c o u n t s o f b o t h m a l e a n d f e m a l e p a r e n t s were p o s i t i v e l y c o r r e l a t e d w i t h mean a g g r e s s i o n s c o r e o f t h e i r p r o g e n y , a t l e a s t u n t i l 3 m o n t h s , w i t h c o r r e l a t i o n s i n v o l v i n g t h e f e m a l e p a r e n t c i r c u l i c o u n t u s u a l l y h i g h e r ( T a b l e 2 0 ) . S i m i l a r l y , t h e l o n g e r b o t h m a l e a n d f e m a l e p a r e n t s s p e n t i n f r e s h w a t e r a s j u v e n i l e s ( i n c r e a s i n g f r e s h w a t e r c i r c u l i number) t h e g r e a t e r t h e w e i g h t l o s s i n 2 0 % o s e a w a t e r a n d t h e l o w e r t h e s u r v i v a l i n 3 0 % o o f t h e i r p r o g e n y ( T a b l e 2 0 ) . I n sum, p a r e n t s w i t h p r o l o n g e d f r e s h w a t e r r e s i d e n c e t e n d e d t o p r o d u c e y o u n g w i t h h i g h a g g r e s s i o n l e v e l s a n d p o o r s a l i n i t y t o l e r a n c e up t o 3 m o n t h s . T h e s e r e l a t i o n s h i p s , h o w e v e r , were s t r o n g l y i n f l u e n c e d by t h e d a t a f o r 1 s t L a k e f a m i l y 3 a n d S q u a m i s h R i v e r , b o t h o f w h i c h h a d a t l e a s t one s t r e a m - t y p e 99 T a b l e 20. C o r r e l a t i o n s b e t w e e n p a r e n t a l f r e s h w a t e r l i f e h i s t o r y , f r o m s c a l e c i r c u l u s c o u n t s , a n d p r o g e n y a g g r e s s i o n a nd s a l i n i t y t o l e r a n c e . *P<0.05, **P<0.01, d f = 7. F e m a l e M a l e Mean Mean % FWC FWC PC 1 S c o r e W e i g h t l o s s M a l e FWC 0.82** Mean PC 1 S c o r e 0.81** 0.50 Mean % w e i g h t l o s s 0.73* 0.64 0.60 Mean % s u r v i v a l - 0 . 7 8 * - 0 . 7 6 * -0.55 - 0 . 9 2 * 100 p a r e n t ( F i g . 1 5 ) . D i s c u s s i o n R h e o t a c t i c b e h a v i o u r C o n s i d e r a b l e . v a r i a t i o n i n r e s p o n s e t o w a t e r c u r r e n t ( r h e o t a x i s ) by j u v e n i l e c h i n o o k s a l m o n i s e v i d e n t f r o m my e x p e r i m e n t s . Not o n l y d i d p o p u l a t i o n s v a r y i n r h e o t a x i s , b u t j u v e n i l e s showed s i g n i f i c a n t c h a n g e s i n r h e o t a x i s w i t h i n c r e a s i n g a g e . A t l e a s t a p o r t i o n o f t h i s v a r i a b i l i t y among e x p e r i m e n t a l g r o u p s a p p e a r s t o be r e l a t e d t o d i f f e r e n c e s i n j u v e n i l e f r e s h w a t e r l i f e h i s t o r y . D i f f e r e n c e s i n r h e o t a x i s b e t w e e n w i l d - r e a r e d , n e w l y - e m e r g e d c h i n o o k f r y f r o m S l i m C r e e k a n d t h e H a r r i s o n R i v e r were c o n s i s t e n t w i t h r e p o r t e d d i f f e r e n c e s i n j u v e n i l e m i g r a t i o n t i m i n g . S l i m C r e e k c h i n o o k summer a n d o v e r w i n t e r i n f r e s h w a t e r b e f o r e s e a w a r d m i g r a t i o n a s y e a r l i n g s a n d t h e y showed l e s s p r o n o u n c e d d o w n s t r e a m movement t h a n H a r r i s o n R i v e r f r y . By c o n t r a s t , g r e a t e r n o c t u r n a l d o w n s t r e a m movement o f H a r r i s o n R i v e r c h i n o o k f r y i n t h e l a b o r a t o r y c h a n n e l s i s c o n s i s t e n t w i t h t h e i r movement d o w s t r e a m t o t h e F r a s e r R i v e r e s t u a r y when n e w l y - e m e r g e d ( F r a s e r e t a l . 1982; L e v y a n d N o r t h c o t e 1 9 8 2 ) . V e r y s i m i l a r r e s u l t s were o b t a i n e d when n e w l y - e m e r g e d f r y were i n c u b a t e d i n t h e l a b o r a t o r y u n d e r i d e n t i c a l c o n d i t i o n s a n d t e s t e d i n t h e r h e o t a x i s a p p a r a t u s . The m a i n t e n a n c e o f t h e s e p h e n o t y p i c d i f f e r e n c e s i n f r y i n c u b a t e d i n i d e n t i c a l e n v i r o n m e n t s s u g g e s t s t h a t t h i s v a r i a t i o n i s , a t l e a s t 101 F i g u r e 15. T r i v a r i a t e p l o t o f t h e r e l a t i v e r a n k s o f mean p a r e n t a l f r e s h w a t e r c i r c u l i c o u n t a n d t h e r a n k s o f a g g r e s s i v e b e h a v i o u r a n d s a l i n i t y t o l e r a n c e o f t h e i r p r o g e n y . A g g r e s s i o n s c o r e s a nd p e r c e n t a g e w e i g h t l o s s a r e a v e r a g e d o v e r 3 months o f age f o r e a c h g r o u p . F1 t h r o u g h F5 a r e l o w e r Nanaimo f a m i l i e s , L1 t h r o u g h L3 a r e 1 s t L a k e f a m i l i e s , SQ i s S q u a m i s h R i v e r . 103 i n p a r t , g e n e t i c a l l y c o n t r o l l e d . The i n c l u s i o n o f d a t a f r o m l a b o r a t o r y - i n c u b a t e d f r y f r o m E a g l e and Nanaimo r i v e r s d i d n o t s u p p o r t t h e h y p o t h e s i s t h a t f r e s h w a t e r l i f e h i s t o r y a c t s t o p r o m o t e d i v e r g e n c e i n r h e o t a x i s . F o r i n s t a n c e , C a r l a n d H e a l e y ( 1 984) s u g g e s t e d t h a t l o w e r Nanaimo R i v e r c h i n o o k f r y m i g r a t e t o t h e e s t u a r y s o o n a f t e r e m e r g e n c e , b u t Nanaimo R i v e r f r y e x h i b i t e d r h e o t a c t i c b e h a v i o u r s i m i l a r t o s t r e a m - t y p e f r y . The e x p l a n a t i o n may l i e i n l o c a l c o n d i t i o n s u n r e l a t e d t o and more i n f l u e n t i a l t h a n t h e d u r a t i o n o f f r e s h w a t e r r e s i d e n c e . F o r i n s t a n c e , t h e Nanaimo R i v e r e s t u a r y i s w i t h i n 5 km o f t h e l o w e r s p a w n i n g a r e a . To r e a c h t h e e s t u a r y s o o n a f t e r e m e r g e n c e , c h i n o o k f r y f r o m t h e l o w e r Nanaimo r i v e r p o p u l a t i o n p r o b a b l y do n o t r e q u i r e a s s t r o n g a d o w n s t r e a m r e s p o n s e a s t h o s e f r o m o t h e r o c e a n - t y p e p o p u l a t i o n s w i t h l o n g e r m i g r a t i o n d i s t a n c e s . F o r i n s t a n c e , H a r r i s o n R i v e r f r y must m i g r a t e a b o u t 100 km t o t h e F r a s e r R i v e r e s t u a r y . F o r Nanaimo R i v e r f r y a more g r a d u a l d o w n s t r e a m d r i f t , s i m i l a r t o t h e b e h a v i o u r o f S l i m C r e e k a n d E a g l e R i v e r f r y , w o u l d a c c o m p l i s h m i g r a t i o n i n a s h o r t t i m e . H o a r ( 1 9 7 6 ) r e p o r t e d t h a t n e w l y - e m e r g e d c h i n o o k f r y r e q u i r e some a c c l i m a t i o n t i m e f o r s u r v i v a l a t s a l i n i t i e s a b o v e 15%©. S i n c e s a l i n i t i e s i n t h e Nanaimo R i v e r e s t u a r y a r e commonly a b o v e 2 0 % o ( H e a l e y 1980) a more g r a d u a l movement i n t o t h e e s t u a r y by Nanaimo f r y may be n e c e s s a r y t o p r e v e n t o s m o r e g u l a t o r y s h o c k . H e a l e y ( 1 9 8 0 ) a l s o r e p o r t e d t h a t mean w e i g h t s o f c h i n o o k f r y 104 e n t e r i n g t h e Nanaimo e s t u a r y were a b o u t 0.57 g. The l a b o r a t o r y -i n c u b a t e d , n e w l y - e m e r g e d s a l m o n u s e d i n my t e s t s were a b o u t 20% l i g h t e r ( 0 . 3 0 - 0 . 5 3 g) a n d Nanaimo R i v e r c h i n o o k l o s t up t o 15% body w e i g h t when e x p o s e d t o 20%<> s e a w a t e r ( F i g . 1 3 a ) . T h u s , a s a c o n s e q u e n c e o f t h e d i f f e r e n t m i g r a t i o n d i s t a n c e s t o t h e i r r e s p e c t i v e e s t u a r i e s , o c e a n - t y p e c h i n o o k f r o m t h e Nanaimo a n d H a r r i s o n r i v e r s a p p e a r t o be g e n e t i c a l l y d i s t i n c t i n t h e i r manner o f d o w n s t r e a m m i g r a t i o n a s n e w l y - e m e r g e d f r y . A l t e r n a t i v e l y , n o c t u r n a l d o w n s t r e a m d i s p e r s a l t o f r e s h w a t e r r e a r i n g a r e a s i s commonly o b s e r v e d i n n e w l y emerged f r y o f v a r i o u s s t r e a m r e s i d e n t s a l m o n i d s ( e . g . R e i m e r s 1973; R a n d a l l 1982; E l l i o t 1986; N a e s j e e t a l . 1986; S h e p h e r d e t a l . 1 9 8 6 b ) . C o n s e q u e n t l y , c u r r e n t r e s p o n s e t e s t s may n o t h a v e been a b l e t o d i s t i n g u i s h b e t w e e n a g r a d u a l " d r i f t m i g r a t i o n " d o w n s t r e a m a t n i g h t by e s t u a r y bound Nanaimo R i v e r c h i n o o k f r y a n d a g r a d u a l d o w n s t r e a m " d i s p e r s a l " f o l l o w i n g e m e r g e n c e by . s t r e a m - t y p e c h i n o o k s . Whereas t e s t s w i t h n e w l y - e m e r g e d f r y y i e l d e d no c l e a r d i s t i n c t i o n i n r h e o t a x i s b a s e d on j u v e n i l e l i f e h i s t o r y , d i f f e r e n c e s i n r h e o t a x i s were o b s e r v e d b e t w e e n s t r e a m - a n d o c e a n - t y p e c h i n o o k when t e s t e d o v e r a f u l l y e a r . S t r e a m - t y p e c h i n o o k s showed p r o n o u n c e d r e d u c t i o n i n p o s i t i v e r h e o t a x i s d u r i n g n o c t u r n a l t e s t s a t 1 y e a r , when, i n n a t u r e , , t h e y s m o l t a n d m i g r a t e s e a w a r d ( C a r l a nd H e a l e y 1984; S h e p h e r d e t a l . I 9 8 6 a , b ) . By c o n t r a s t , l a b o r a t o r y - r e a r e d , o c e a n - t y p e 105 c h i n o o k a p p e a r e d t o be s e n s i t i v e t o w a t e r c u r r e n t o n l y d u r i n g t h e i r f i r s t 2-3 months o r a b o u t 2-5 g i n w e i g h t when, i n n a t u r e , t h e y t o o w o u l d m i g r a t e t o e s t u a r i n e a r e a s ( R e i m e r s 1973; F r a s e r e t a l . 1982; C a r l a n d H e a l e y 1 9 8 4 ) . The c o r r e s p o n d e n c e b e t w e e n t h e i r l a b o r a t o r y " m i g r a t i o n " b e h a v i o u r a n d t h e i r m i g r a t i o n t i m i n g i n t h e w i l d s u g g e s t s t h a t t h e i n h e r i t e d d i f f e r e n c e s i n r h e o t a x i s a r e a d a p t i v e a n d a f u n c t i o n o f d i v e r g e n c e b e t ween c h i n o o k p o p u l a t i o n s i n f r e s h w a t e r r e a r i n g l i f e h i s t o r y ( i . e . s t r e a m - v s o c e a n - t y p e l i f e h i s t o r i e s ) . A g g r e s s i v e b e h a v i o u r L e v e l s o f a g g r e s s i v e b e h a v i o u r were a l s o c l o s e l y r e l a t e d t o f r e s h w a t e r l i f e h i s t o r y i n c h i n o o k s a l m o n . • F i s h f r o m p o p u l a t i o n s o r f a m i l i e s t h a t r e s i d e f o r e x t e n d e d p e r i o d s i n f r e s h w a t e r were more a g g r e s s i v e t h a n t h o s e t h a t a b a n d o n i t a t an e a r l y a g e . The r e l a t i o n s h i p b e t w e e n l i f e h i s t o r y p a t t e r n a n d a g g r e s s i v e b e h a v i o u r was c o n s i s t e n t among p o p u l a t i o n s f r o m d i f f e r e n t r i v e r s , b e t w e e n p o p u l a t i o n s w i t h i n a s i n g l e r i v e r , a n d among f a m i l i e s w i t h i n a p o p u l a t i o n , a l t h o u g h t h e l a t t e r d i f f e r e n c e s were m i n o r r e l a t i v e t o i n t e r p o p u l a t i o n d i f f e r e n c e s . The g r e a t e r a g g r e s s i v e n e s s o f s t r e a m - t y p e c h i n o o k was a p p a r e n t b o t h i n w i l d f i s h a n d t h o s e i n c u b a t e d a n d r e a r e d i n a common l a b o r a t o r y e n v i r o n m e n t . T h e r e f o r e , t h e v a r i a t i o n i n b e h a v i o u r i s , i n p a r t , b a s e d upon g e n e t i c d i f f e r e n c e s among p o p u l a t i o n s . E v e n w i t h i n a p o p u l a t i o n , c h a n g e s i n a g g r e s s i v e b e h a v i o u r w i t h age c o r r e l a t e w e l l w i t h t e m p o r a l s h i f t s i n r e a r i n g h a b i t a t 1 06 ( F i g . 8 a , b ) ; t h e p r o n o u n c e d d e c l i n e i n a g g r e s s i v e b e h a v i o u r i n 1 s t L a k e c h i n o o k s a t 3 months ( 3 . 9 g) c o r r e s p o n d s w i t h t h e i r m i g r a t i o n t o t h e e s t u a r y a t t h i s t i m e (3.5-4.1 g) and t h e s h i f t t o a more p e l a g i c e x i s t e n c e ( H e a l e y 1980; H e a l e y a n d J o r d a n 1982; C a r l a n d H e a l e y 1 9 8 4 ) . By 3 months a n d a t 6 m o n t h s , t h e S l i m C r e e k , s t r e a m - t y p e j u v e n i l e s were more a g g r e s s i v e t h a n o c e a n - t y p e f i s h f r o m t h e Nanaimo R i v e r . I n sum, a g g r e s s i v e b e h a v i o u r c o r r e l a t e s w e l l w i t h t h e d i f f e r e n c e s i n s m o l t i f i c a t i o n a n d m i g r a t i o n t i m i n g among t h e g r o u p s o f c h i n o o k s a l m o n i n v e s t i g a t e d . E a r l i e s t m i g r a t i n g j u v e n i l e s were l e a s t a g g r e s s i v e a n d showed t h e e a r l i e s t d e c l i n e s i n a g g r e s s i v e b e h a v i o u r w h e r e a s s a l m o n t h a t m i g r a t e l a t e r m a i n t a i n e d t h e h i g h e s t a g g r e s s i o n l e v e l s . S a l m o n i d s w i t h e x t e n d e d r e s i d e n c e i n s t r e a m s h a v e w e l l d e f i n e d t e r r i t o r i e s ( K e e n l e y s i d e 1 9 7 9 ) , w h i c h c o n f e r a d v a n t a g e s i n f e e d i n g e f f i c i e n c y ( A l l e n 1969; K e e n l e y s i d e 1979; F a u s c h 1984) and p r o t e c t i o n f r o m p r e d a t i o n ( A l l e n 1969; Symons 1 9 7 4 ) . T e r r i t o r y f o r m a t i o n a n d m a i n t e n a n c e i n v o l v e s i t e f i d e l i t y a n d d e f e n c e by e x p u l s i o n o f i n t r u d e r s w i t h o v e r t a g g r e s s i o n , d i s p l a y s , o r b o t h ( K e e n l e y s i d e 1 9 7 9 ) . A g g r e s s i v e b e h a v i o u r m u s t , t h e r e f o r e , be an i m p o r t a n t component o f e x t e n d e d s t r e a m r e s i d e n c e . By c o n t r a s t , m i g r a t i n g f i s h o f t e n s c h o o l , w h i c h p r o b a b l y i n v o l v e s g r e a t e r s o c i a l t o l e r a n c e . I s u g g e s t , t h e r e f o r e , t h a t t h e g e n e t i c d i f f e r e n c e s i n a g g r e s s i v e b e h a v i o u r among c h i n o o k s a l m o n p o p u l a t i o n s r e s u l t s , . i n p a r t , f r o m s e l e c t i o n a c t i n g t h r o u g h t h e f u n c t i o n a l a s s o c i a t i o n s among 107 d u r a t i o n o f s t r e a m r e s i d e n c e , t e r r i t o r i a l i t y , a n d a g g r e s s i o n . D i v e r g e n c e b e t w e e n c h i n o o k s a l m o n l i f e h i s t o r y - t y p e s may r e s u l t f r o m h i g h a g g r e s s i o n b e i n g f a v o u r e d i n t e r r i t o r i a l , s t r e a m - t y p e p o p u l a t i o n s w h e r e a s low a g g r e s s i o n i s f a v o u r e d i n e a r l y m i g r a t i n g , o c e a n - t y p e p o p u l a t i o n s . R e i m e r s ( 1 9 6 8 ) n o t e d t h a t o c e a n - t y p e c h i n o o k f r y i n t h e S i x e s R i v e r ( O r e g o n ) e s t u a r y s w i t c h e d f r o m a g g r e g a t i v e , p a s s i v e b e h a v i o u r on f l o o d t i d e t o t e r r i t o r i a l , a g g r e s s i v e b e h a v i o u r on ebb t i d e . U n d e r more c o n s t a n t c o n d i t i o n s o f r i v e r f l o w , h o w e v e r , n a t u r a l s e l e c t i o n m i g h t f a v o u r h i g h l e v e l s o f a g g r e s s i v e b e h a v i o u r i n s t r e a m - t y p e c h i n o o k . The a s s o c i a t i o n b e t w e e n f r e s h w a t e r l i f e h i s t o r y a n d a g g r e s s i v e b e h a v i o u r i n c h i n o o k s a l m o n i s s u p p o r t e d by work on o t h e r f i s h . F o r i n s t a n c e , F e r g u s o n a n d N o a k e s ( 1 9 8 2 , I 9 8 3 a , b ) d e m o n s t r a t e d t h a t b r o o k c h a r r ( S a l v e l i n u s f o n t i n a l i s ) , a t e r r i t o r i a l s t r e a m - d w e l l e r , i s more a g g r e s s i v e t h a n t h e l a k e c h a r r ( S . n a m a y c u s c h ) , a more w i d e l y - r o a m i n g l a c u s t r i n e s p e c i e s , a n d t h a t t h e s e b e h a v i o u r a l d i f f e r e n c e s were i n h e r i t e d . A l s o , f o r t h r e e s p i n e s t i c k l e b a c k , G a s t e r o s t e u s a c u l e a t u s , B a k k e r a n d F e u t h - d e B r u i j n ( 1 9 8 8 ) f o u n d t h a t p e r m a n e n t r e s i d e n t s o f f r e s h w a t e r were more a g g r e s s i v e t h a n t h e i r a nadromous c o u n t e r p a r t s . More g e n e r a l l y , a g g r e s s i v e b e h a v i o u r o f t e n a p p e a r s t o be c o r r e l a t e d w i t h d i f f e r e n c e s i n l i f e h i s t o r y i n s e v e r a l t a x a ( e . g . m a t i n g s y s t e m v a r i a t i o n i n b i r d s ( W i n g f i e l d e t a l . 1 9 8 7 ) , v a r i a t i o n i n i n t e n s i t y o f i n t e r s p e c i f i c c o m p e t i t i o n i n s a l a m a n d e r s ( N i s h i k a w a 1 9 8 5 ) , a n d h a b i t a t 108 v a r i a t i o n i n f i s h e s ( P a r z e f a l l 1 9 8 6 ) ) . M o r p h o l o g y W i t h t h e e x c e p t i o n o f m a j o r p a r r mark number, m o r p h o l o g i c a l d i f f e r e n c e s b e t w e e n w i l d c h i n o o k f r y f r o m t h e H a r r i s o n R i v e r a n d S l i m C r e e k were m a i n t a i n e d i n t h e l a b o r a t o r y - r e a r e d f r y ; S l i m f r y h a d l a r g e r body p a r t s a n d m e d i a n f i n s a n d were more b r i g h t l y c o l o u r e d ( T a b l e 9 ) . A s i g n i f i c a n t e n v i r o n m e n t a l component t o p a r r mark number i s s u g g e s t e d s i n c e S l i m a n d H a r r i s o n f r y had s i m i l a r c o u n t s when b o t h were i n c u b a t e d a n d r e a r e d i n t h e same l a b o r a t o r y e n v i r o n m e n t . I n c u b a t i o n w a t e r t e m p e r a t u r e r e g i m e c a n a l t e r p a r r mark c o u n t s i n c h i n o o k f r y ; l o w e r w a t e r t e m p e r a t u r e s p r o d u c e h i g h e r c o u n t s ( C O . L i n d s e y a n d E.B. T a y l o r , u n p u b l . d a t a ) . T h e r e f o r e , w a t e r t e m p e r a t u r e d i f f e r e n c e s i n t h e i n c u b a t i o n e n v i r o n m e n t s o f t h e H a r r i s o n R i v e r a n d S l i m C r e e k ( c o l d e r ) p r o b a b l y a c c o u n t f o r t h e g r e a t e r d i f f e r e n c e s i n p a r r mark number i n w i l d f r y . D e s p i t e t h e i n h e r i t e d d i f f e r e n c e s i n m o r p h o l o g y b e t w e e n c h i n o o k f r y f r o m S l i m C r e e k a n d t h e H a r r i s o n R i v e r , t h e i n c l u s i o n o f d a t a f o r E a g l e a n d Nanaimo c h i n o o k s d i d n o t s u p p o r t a g e n e r a l m o r p h o l o g i c a l d i s t i n c t i o n w i t h i n c h i n o o k s a l m o n b a s e d on j u v e n i l e l i f e h i s t o r y p a t t e r n . Whereas S l i m C r e e k f r y had t h e l a r g e s t body p a r t s a n d m e d i a n f i n s a n d were t h e most c o l o u r f u l f r y , t h o s e f r o m b o t h o c e a n - t y p e p o p u l a t i o n s t e n d e d t o h a v e l a r g e r f i n s t h a n E a g l e R i v e r c h i n o o k f r y . F u r t h e r m o r e , 109 Nanaimo R i v e r f r y were a s b r i g h t l y c o l o u r e d a s were t h o s e f r o m t h e E a g l e R i v e r . A g a i n , l o c a l p o p u l a t i o n f a c t o r s u n r e l a t e d t o d u r a t i o n o f f r e s h w a t e r r e a r i n g may a c c o u n t f o r t h e m o r p h o l o g i c a l d i f f e r e n c e s among t h e p o p u l a t i o n s o f n e w l y - e m e r g e d c h i n o o k f r y . S e l e c t i o n a s s o c i a t e d w i t h m i g r a t i o n d i s t a n c e , w a t e r f l o w l e v e l s , a n d p r e d a t i o n h a v e been a s s o c i a t e d w i t h i n t e r p o p u l a t i o n d i f f e r e n c e s i n m o r p h o l o g y a n d c o l o u r a t i o n i n s t r e a m f i s h e s ( L i l e y a n d S e g h e r s 1975; E n d l e r 1980; R i d d e l l a n d L e g g e t t 1981; T a y l o r a n d M c P h a i l I 9 8 5 a , b ) . G r o w t h r a t e I n t h e l a b o r a t o r y , o c e a n - t y p e c h i n o o k grew f a s t e r t h a n s t r e a m - t y p e . W i t h l e r e t a l . ( 1 9 8 7 ) a l s o d e t e c t e d s i g n i f i c a n t g e n e t i c v a r i a t i o n i n g r o w t h r a t e among c h i n o o k s a l m o n p o p u l a t i o n s a n d i n t h e i r s t u d y o c e a n - t y p e s a l m o n grew f a s t e r t h a n c h i n o o k f r o m s t r e a m - t y p e p o p u l a t i o n s . Among a n a d r o m o u s s a l m o n i d s , l a r g e r i n d i v i d u a l s r e g u l a t e e l e c t r o l y t e s b e t t e r a n d have h i g h e r s u r v i v a l r a t e s d u r i n g s e a w a t e r " c h a l l e n g e " t e s t s ( P a r r y 1960; C o n t e a n d Wagner 1965; C o n t e e t a l . 1966; M c C o r m i c k a n d Naiman 1984b; C l a r k e a n d S h e l b o u r n 1 9 8 5 ) , a n d s m a l l e r o n e s a r e more s u s c e p t i b l e t o p r e d a t i o n i n n e a r s h o r e m a r i n e h a b i t a t s ( P a r k e r 1971; M a r t i n e t a l . 1981; H e a l e y 1982; H a r g r e a v e s a nd L e b r a s s e u r 1 9 8 6 ) . T h e s e o b s e r v a t i o n s s u g g e s t t h a t , a s u n d e r y e a r l i n g s , t h e e a r l i e r m i g r a t i n g , o c e a n - t y p e c h i n o o k s a l m o n may be u n d e r s t r o n g 1 10 s e l e c t i o n f o r f a s t g r o w t h w h i c h m i g h t e x p l a i n t h e i r h i g h e r g r o w t h r a t e s c o m p a r e d t o s t r e a m - t y p e f i s h . S a l i n i t y t o l e r a n c e Once s i z e v a r i a t i o n among t h e e x p e r i m e n t a l g r o u p s o f c h i n o o k s a l m o n was a c c o u n t e d f o r , s i g n i f i c a n t i n t e r f a m i l y v a r i a t i o n was d e t e c t e d i n b o t h w e i g h t l o s s i n 20%© s e a w a t e r a nd s u r v i v a l i n 3 0 % o s e a w a t e r . J u v e n i l e c h i n o o k f r o m t h e l o w e r Nanaimo R i v e r s p a w n i n g p o p u l a t i o n r a n k e d b e t t e r t h a n 1 s t L a k e c h i n o o k s i n t e r m s o f s a l i n i t y t o l e r a n c e , b u t v a r i a b i l i t y among f a m i l i e s w i t h i n p o p u l a t i o n s was g r e a t e r s u c h t h a t no s i g n i f i c a n t d i f f e r e n c e s i n s a l i n i t y t o l e r a n c e a t t r i b u t a b l e t o s p a w n i n g p o p u l a t i o n were d e t e c t e d . The l o w s a l i n i t y t o l e r a n c e o f S q u a m i s h R i v e r c h i n o o k r e l a t i v e t o Nanaimo r i v e r c h i n o o k s , h o w e v e r , s u g g e s t s t h a t d i f f e r e n c e s b e t w e e n p o p u l a t i o n s f r o m d i f f e r e n t r i v e r s y s t e m s may e x i s t . V a r i a b i l i t y i n s i z e - a d j u s t e d s a l i n i t y t o l e r a n c e was b r o a d l y r e l a t e d t o j u v e n i l e l i f e h i s t o r y p a t t e r n . B o t h s t r e a m - t y p e j u v e n i l e s f r o m S q u a m i s h R i v e r a n d 1 s t L a k e f a m i l y 3 were s a l i n i t y i n t o l e r a n t up u n t i l 3 months w h i c h i s c o n s i s t e n t w i t h t h e e x t e n d e d f r e s h w a t e r r e s i d e n c e o f t h e i r p a r e n t s ( T a b l e 1 5 ) . By c o n t r a s t , . p r o g e n y f r o m l o w e r Nanaimo f a m i l i e s 4 a n d 5 (whose p a r e n t s h a d t h e s h o r t e s t f r e s h w a t e r r e s i d e n c e ) p e r f o r m e d b e s t i n s e a w a t e r a t emergence a n d i n c r e a s e d t h e i r p e r f o r m a n c e most 111 r a p i d l y w i t h a g e . S i z e v a r i a t i o n i s s u s p e c t e d t o be a p r i m a r y f a c t o r i n f l u e n c i n g s u r v i v a l , r e p r o d u c t i v e s u c c e s s a n d , h e n c e , f i t n e s s i n f i s h p o p u l a t i o n s ( S c h a f f e r a n d E l s o n 1975; O l i v e r e t a l . 1979; R e i s e n b i c h l e r e t a l . 1982; H e a l e y a n d H e a r d 1984; M i l l e r e t a l . 1 9 8 8 ) . I n s a l m o n i d s , l a r g e r f e m a l e s t e n d t o p r o d u c e l a r g e r e g g s and l a r g e r n e w l y - e m e r g e d f r y (Brown 1946; F o w l e r 1972; G a l l 1974; Beacham e t a l . 1985; F i g . 1 1 ) , a n d t h e l a r g e r f r y m a i n t a i n t h e i r s i z e a d v a n t a g e f o r v a r i a b l e t i m e p e r i o d s (Brown 1946; F o w l e r 1972; G a l l 1974; T a y l o r u n p u b l . ) . M a t e r n a l e f f e c t s ( t h r o u g h f e m a l e s i z e / e g g s i z e a n d egg s i z e / f r y s i z e r e l a t i o n s h i p s ) p r o b a b l y i n f l u e n c e s i z e - d e p e n d e n t f r y s u r v i v a l . S i z e a t m a t u r i t y i n f i s h i s known t o be a t l e a s t p a r t i a l l y u n d e r g e n e t i c c o n t r o l ( R i c k e r 1972; A l l e n d o r f e t a l . 1983; S t e a r n s 1 9 8 3 ) . T h e r e f o r e , b i o c h e m i c a l a d a p t a t i o n s f o r s u r v i v a l i n h i g h s a l i n i t y w a t e r may be s e c o n d a r y t o s e l e c t i o n f o r l a r g e s i z e - a t - e m e r g e n c e i n e a r l y d o w n s t r e a m m i g r a t i n g f r y . The l a r g e r s i z e o f l o w e r Nanaimo f e m a l e s a n d o f t h e i r n e w l y -emerged f r y ( H e a l e y a n d J o r d a n 1982; F i g . 11) may be a d a p t i v e r e s p o n s e s t o t h e c l o s e n e s s o f t h e l o w e r s p a w n i n g a r e a t o t h e e s t u a r y . W h e t h e r d r i v e n l a r g e l y by s e l e c t i o n f o r f r y s i z e - a t -e m e r g e n c e o r by b i o c h e m i c a l a d a p t a t i o n s , t h e v a r i a b i l i t y i n s e a w a t e r p e r f o r m a n c e among t h e g r o u p s o f c h i n o o k s a l m o n i s c o n s i s t e n t w i t h t h e i r d i f f e r e n c e s i n d u r a t i o n o f f r e s h w a t e r r e s i d e n c e a n d , h e n c e , p r o b a b l y r e f l e c t s a d a p t i v e d i v e r s i f i c a t i o n . 1 12 I n t e r r e l a t i o n s h i p s among v a r i a b l e s I n s a l m o n i d s , g r o w t h r a t e may i n f l u e n c e t i m i n g o f d e v e l o p m e n t a l p r o c e s s e s s u c h a s s m o l t i f i c a t i o n ( T h o r p e 1 9 8 6 ) , p e r h a p s t h r o u g h i t s r e l a t i o n s h i p w i t h hormones t h o u g h t t o s y n c h r o n i z e c o m p o n e n t s o f s m o l t i f i c a t i o n ( s e e r e v i e w s by F o l m a r a n d D i c k h o f f 1980; D i c k h o f f a n d S u l l i v a n 1987; H oar 1 9 8 8 ) . I n c r e a s e d g r o w t h r a t e , e l e v a t e d t h y r o i d o r o t h e r hormone l e v e l s , d e c r e a s e d a g g r e s s i v e b e h a v i o u r , a n d i n c r e a s e d m i g r a t o r y r e s t l e s s n e s s o c c u r c o n c u r r e n t l y d u r i n g s m o l t i f i c a t i o n ( F o l m a r a n d D i c k h o f f 1980; D i c k h o f f a n d S u l l i v a n 1987; M c C o r m i c k a n d S a u n d e r s 1987; H oar 1 9 8 8 ) . I n a d d i t i o n , M c C o r m i c k a n d Naiman ( 1 9 8 4 a ) r e p o r t e d a p o s i t i v e c o r r e l a t i o n b e t w e e n g r o w t h r a t e a n d p l a s m a t h y r o x i n e l e v e l s i n b r o o k c h a r r , S a l v e l i n u s f o n t i n a l i s . G o d i n e t a l . ( 1 9 7 4 ) d e m o n s t r a t e d t h a t j u v e n i l e A t l a n t i c s a l m o n i n j e c t e d w i t h t h y r o x i n e showed r e d u c e d a g g r e s s i v e n e s s a n d i n c r e a s e d d o w n s t r e a m o r i e n t a t i o n . The h i g h e r g r o w t h r a t e s o f o c e a n - t y p e c h i n o o k s may be a s s o c i a t e d w i t h e l e v a t e d hormone l e v e l s d u r i n g t h e i r f i r s t few m o n t h s . T h e r e f o r e , g r o w t h r a t e r e l a t e d d i f f e r e n c e s i n hormone d y n a m i c s may a l s o c o n t r i b u t e t o d i f f e r e n c e s i n a g g r e s s i v e b e h a v i o u r b e t w e e n l i f e h i s t o r y t y p e s . L e s s a g g r e s s i v e , e a r l y m i g r a t i n g c h i n o o k f r o m t h e l o w e r Nanaimo R i v e r grew f a s t e r t h a n t h e more a g g r e s s i v e , l a t e r m i g r a t i n g c h i n o o k f r o m 1 s t L a k e o v e r t h e f i r s t 3 months i n t h e l a b o r a t o r y . The a b r u p t d e c l i n e i n 1 1 3 a g g r e s s i v e b e h a v i o u r b e t w e e n 2 a n d 3 months o f age by t h e 1 s t L a k e Nanaimo c h i n o o k j u v e n i l e s was a c c o m p a n i e d by an i n c r e a s e i n s p e c i f i c g r o w t h r a t e . The j u v e n i l e l i f e h i s t o r y t y p e s i n v e s t i g a t e d i n t h i s s t u d y d i f f e r e d g e n e t i c a l l y i n r h e o t a x i s , a g g r e s s i v e b e h a v i o u r , and i n g r o w t h r a t e . F e r g u s o n a n d N o a k e s ( 1 9 8 2 , 1983a,b) d e m o n s t r a t e d g e n e t i c d i f f e r e n c e s i n a g g r e s s i v e b e h a v i o u r a n d m o b i l i t y p a t t e r n s b e t w e e n t h e h i g h l y a g g r e s s i v e and t e r r i t o r i a l b r o o k c h a r r and t h e l e s s a g g r e s s i v e , more m o b i l e l a k e c h a r r . B a s e d on t h e s e s t u d i e s , N oakes ( 1 9 8 6 ) s u g g e s t e d t h a t , f o r S a l v e l i n u s , n a t u r a l s e l e c t i o n may h a v e f a v o r e d t h e i n h e r i t a n c e o f s u i t e s o f c h a r a c t e r s ; one s e t f o r a l i f e h i s t o r y i n v o l v i n g d e f e n c e o f f i x e d t e r r i t o r i e s i n s t r e a m e n v i r o n m e n t s ( b r o o k c h a r r ) a n d a n o t h e r s e t f o r a more f r e e - r a n g i n g , p e l a g i c l i f e s t y l e i n l a c u s t r i n e e n v i r o n m e n t s ( l a k e c h a r r ) . A l s o , E r i k s s o n and L u n d q v i s t ( 1 9 8 5 ) showed t h a t s e a s o n a l c h a n g e s i n r h e o t a x i s a n d s a l i n i t y t o l e r a n c e i n y e a r l i n g A t l a n t i c s a l m o n t e n d e d t o c o i n s i d e . D u r i n g t h e n o r m a l p e r i o d o f s e a w a r d m i g r a t i o n i n t h e w i l d , s a l m o n y e a r l i n g s t e n d e d t o swim d o w n s t r e a m i n a l a b o r a t o r y a p p a r a t u s and showed a n n u a l p e a k s i n t o l e r a n c e t o 2 0 % o s e a w a t e r . As t h e s e a s o n a l p e a k i n d o w n s t r e a m m i g r a t i o n i n w i l d p o p u l a t i o n s t a i l e d o f f , l a b o r a t o r y - r e a r e d f i s h showed an i n c r e a s i n g t e n d e n c y t o swim u p s t r e a m a n d t h e y became i n c r e a s i n g l y i n t o l e r a n t o f s e a w a t e r ( E r i k s s o n a n d L u n d q v i s t 1 9 8 5 ) . 1 1 4 N a t u r a l s e l e c t i o n o p e r a t i n g on s e t s o f t r a i t s w i t h c l o s e f u n c t i o n a l r e l a t i o n s h i p s t o i n c r e a s e t h e f i t n e s s o f a p h e n o t y p e ( G o u l d a n d L e w o n t i n 1979; A r n o l d 1983; Mayr 1983) h a s been s u g g e s t e d i n s t u d i e s on f o r a g i n g b e h a v i o u r a n d t r o p h i c m o r p h o l o g y ( E c h e l l e a n d K o r n f i e l d 1984; L a v i n a n d M c P h a i l 1986, 1 9 8 7 ) , a n d r e p r o d u c t i v e c h a r a c t e r s ( S t e a r n s 1983; H e a l e y 1987) i n f i s h e s . D i f f e r e n t i a l e x p r e s s i o n o f s u i t e s o f b e h a v i o u r s i s a l s o c h a r a c t e r i s t i c o f i n d i v i d u a l A t l a n t i c s a l m o n a d o p t i n g a l t e r n a t i v e l i f e h i s t o r i e s ( M e t c a l f e e t a l . 1988; M e t c a l f e 1989; M e t c a l f e e t a l . 1 9 8 9 ) . S i m i l a r i n t e g r a t i o n o f j u v e n i l e p h e n o t y p e p r o b a b l y o c c u r s i n c h i n o o k s a l m o n where s e l e c t i o n f a v o u r s l o w a g g r e s s i v e n e s s , a weak s e a s o n a l r h e o t a c t i c r e s p o n s e , h i g h g r o w t h r a t e , a n d h i g h s a l i n i t y t o l e r a n c e i n e a r l y m i g r a t i n g , o c e a n - t y p e c h i n o o k w h i l e f a v o r i n g h i g h a g g r e s s i v e n e s s , a p r o n o u n c e d s e a s o n a l r h e o t a c t i c r e s p o n s e , s l o w e r g r o w t h r a t e , a n d d e l a y e d s a l t w a t e r t o l e r a n c e a b i l i t y i n s t r e a m - t y p e c h i n o o k s . 1 15 CHAPTER 2: GEOGRAPHIC VARIATION I N , AND ENVIRONMENTAL CORRELATES OF, J U V E N I L E CHINOOK SALMON L I F E HISTORY I n t r o d u c t i o n The g e o g r a p h i c d i s t r i b u t i o n o f s p e c i e s , a n d p h e n o t y p i c d i f f e r e n c e s among p o p u l a t i o n s o f s p e c i e s , h a v e been i m p o r t a n t s o u r c e s f o r i n f e r e n c e s a b o u t e v o l u t i o n a r y c h a n g e a nd t h e p r o c e s s o f s p e c i a t i o n (Mayr 1963; G o u l d a n d J o h n s o n 1972; W r i g h t 1 9 7 8 ) . G e o g r a p h i c v a r i a t i o n i s one o f t h e most f u n d a m e n t a l b i o l o g i c a l o b s e r v a t i o n s f o r i t p r o m p t s t h e o b s e r v e r t o a s k how s u c h v a r i a b i l i t y c o u l d h a v e a r i s e n o r c o u l d be m a i n t a i n e d . A t t e m p t s t o a n s w e r s u c h q u e s t i o n s h a v e l a i d t h e f o u n d a t i o n f o r c u r r e n t c o n c e p t s a n d u n d e r s t a n d i n g o f e v o l u t i o n a r y a n d e c o l o g i c a l t h e o r y ( G o u l d a n d J o h n s o n 1972; L e w o n t i n 1974; E n d l e r 1977; A r t h u r 1982; F u t u y m a 1 9 8 6 ) . The s t u d y o f g e o g r a p h i c v a r i a t i o n i s a l s o c e n t r a l t o t h e s t u d y o f a d a p t a t i o n a s an e v o l u t i o n a r y c o n s e q u e n c e o f n a t u r a l s e l e c t i o n ( e . g . J o h n s o n a n d S e l a n d e r 1971; E n d l e r 1986; E t t e r 1 9 8 8 ) . I n s a l m o n i d f i s h e s , t h e s t u d y o f g e o g r a p h i c v a r i a t i o n h a s been e x t e n s i v e b e c a u s e o f t h e w i d e a r r a y o f e n v i r o n m e n t s i n t h e g e o g r a p h i c r a n g e o f t h e v a r i o u s s p e c i e s a n d t h e t e n d e n c y o f a d u l t s t o r e t u r n t o t h e i r n a t a l s t r e a m s t o spawn. S t u d i e s o f i n t r a s p e c i f i c g e o g r a p h i c v a r i a t i o n h a v e f o c u s s e d on a v a r i e t y o f t r a i t s i n c l u d i n g a l l o z y m e f r e q u e n c i e s ( T h o r p e a n d M i t c h e l l 1981; Wehrhahn a n d P o w e l l 1 9 8 6 ) , m i t o c h o n d r i a l DNA ( B i r t e t a l . 1 9 8 6 ) , 116 d e v e l o p m e n t a l r a t e (Beacham a n d M u r r a y 1 9 8 6 ) , s c a l e g r o w t h c h a r a c t e r s ( L e a r and M i s r a 1 9 7 8 ) , m o r p h o l o g y and m e r i s t i c s ( C a v e n d e r 1978; S v a r d s o n 1979; C l a y t o r and MacCrimmon 1 9 8 8 ) , a n d l i f e h i s t o r y t r a i t s ( S c h a f f e r a n d E l s o n 1975; H e a l e y a n d H e a r d 1984; M y e r s 1 9 8 6 ) . A m a j o r g o a l o f many s u c h s t u d i e s h a s been n o t j u s t t o d e s c r i b e t h e r a n g e o f v a r i a b i l i t y , b u t t o e x p l a i n t h e v a r i a t i o n i n t h e c o n t e x t o f c u r r e n t e v o l u t i o n a r y a n d l i f e h i s t o r y t h e o r y ( e . g . A s p i n w a l l 1974; S c h a f f e r a n d E l s o n 1975; A l t u k h o v 1982; H e a l e y a n d H e a r d 1 9 8 4 ) . W h i l e g e n e r a l a p p r e c i a t i o n o f g e o g r a p h i c v a r i a b i l i t y i n j u v e n i l e l i f e h i s t o r i e s , b o t h b e t ween and w i t h i n s p e c i e s , h a s a l o n g h i s t o r y i t i s o n l y r e c e n t l y t h a t s y s t e m a t i c s t u d i e s have been i n i t i a t e d ( W i t h l e r 1966; Power 1981; R a n d a l l e t a l . 1987; M e t c a l f e and T h o r p e 1 9 8 9 ) . I n C h a p t e r 1 o f t h i s t h e s i s , t h e r a n g e o f v a r i a b i l i t y i n f r e s h w a t e r l i f e h i s t o r y o f c h i n o o k s a l m o n was i n t r o d u c e d and e v i d e n c e was p r e s e n t e d t h a t t h i s v a r i a b i l i t y r e p r e s e n t s i n t r a s p e c i f i c a d a p t i v e d i v e r g e n c e . T h i s c h a p t e r d e a l s w i t h two f u r t h e r a s p e c t s o f v a r i a b i l i t y i n j u v e n i l e l i f e h i s t o r y . F i r s t , i t d i s c u s s e s v a r i a b i l i t y i n j u v e n i l e l i f e h i s t o r y i n c o n t e x t w i t h t h e g e o g r a p h i c d i s t r i b u t i o n o f c h i n o o k s a l m o n . S e c o n d , i t p r e s e n t s r e s u l t s o f a s s o c i a t i o n a n a l y s e s b e t w e e n v a r i a t i o n i n j u v e n i l e l i f e h i s t o r y a n d a b i o t i c e n v i r o n m e n t a l f a c t o r s i n an a t t e m p t t o d e t e r m i n e t h e c a u s e s o f v a r i a t i o n i n j u v e n i l e p h e n o t y p e . B i o t i c f a c t o r s , p r i m a r i l y i n t h e c o n t e x t o f c o m p e t i t i v e i n t e r a c t i o n s w i t h o t h e r s p e c i e s , a r e t h e s u b j e c t o f i n v e s t i g a t i o n i n Chapter 118 1. GEOGRAPHIC DISTRIBUTION OF CHINOOK SALMON AND VARIATION I N L I F E HISTORY M e t h o d s D a t a c o n c e r n i n g g e o g r a p h i c v a r i a t i o n i n j u v e n i l e c h i n o o k f r e s h w a t e r l i f e h i s t o r y p a t t e r n were d e r i v e d f r o m t h r e e s o u r c e s : ( i ) s u r v e y s o f t h e l i t e r a t u r e , ( i i ) p e r s o n a l c o m m u n i c a t i o n s o r u n p u b l i s h e d d a t a f r o m C a n a d i a n a n d U.S. G o v e r n m e n t f i s h e r i e s b i o l o g i s t s , a n d ( i i i ) f o r B.C. a n d Yukon p o p u l a t i o n s , a s u r v e y o f t h e s c a l e d a t a b a s e a t t h e S c a l e M o r p h o l o g y L a b . D u r i n g t h e s u r v e y s o f t h e s c a l e d a t a , an e f f o r t was made t o n o t e p o t e n t i a l b i a s e s i n t h e mode o f c o l l e c t i o n o f s c a l e s . F o r i n s t a n c e , most s c a l e s a m p l e s were t a k e n f r o m a d u l t s a l m o n h o l d i n g i n p o o l s b e f o r e s p a w n i n g , f r o m a d u l t s e n u m e r a t e d a t c o u n t i n g f e n c e s , o r f r o m a d u l t c a r c a s s e s s a m p l e d a f t e r s p a w n i n g . C o l l e c t i o n m e t h o d o l o g y c o u l d b i a s t h e s e x u a l c o m p o s i t i o n o f s a m p l e s w i t h a p o t e n t i a l i n f l u e n c e on s u b s e q u e n t f r e s h w a t e r age d i s t r i b u t i o n s . H o wever, t h i s d o e s n o t seem t p h a v e been a s e r i o u s s o u r c e o f e r r o r . F o r e x a m p l e , S n y d e r ( 1 9 3 1 ) e x a m i n e d t h e s c a l e s o f m a l e a n d f e m a l e c h i n o o k s a l m o n r e t u r n i n g t o spawn i n t h e K l a m a t h R i v e r , C a l i f o r n i a , o v e r f o u r y e a r s b e t w e e n 1919 a n d 1930. S n y d e r ' s d a t a i n d i c a t e r o u g h l y e q u a l p r o p o r t i o n s o f s t r e a m - a n d o c e a n - t y p e l i f e h i s t o r i e s b e t w e e n t h e s e x e s ( a p p r o x i m a t e l y 13 a n d 11% s t r e a m - t y p e r e s p e c t i v e l y ) . C l a r k ' s ( 1 9 2 9 ) d a t a f o r S a c r a m e n t o R i v e r c h i n o o k s a l m o n were s i m i l a r 119 w i t h p e r h a p s a s l i g h t l y g r e a t e r p r o p o r t i o n o f s t r e a m - t y p e l i f e h i s t o r i e s i n f e m a l e s (12 v s 8 % ) . A s i m i l a r t r e n d was e v i d e n t f o r M o n t e r e y Bay f i s h e r y s a m p l e s ; m a l e s = 1 7 . 3 % s t r e a m - t y p e , f e m a l e s = 1 9 . 3 % s t r e a m - t y p e ( C l a r k 1 9 2 9 ) . S c a l e s a m p l e s f r o m m a l e a n d f e m a l e c h i n o o k s a l m o n s p a w n i n g i n t r i b u t a r i e s o f t h e F r a s e r R i v e r , a n d i n s t r e a m s i n s o u t h c o a s t a l B.C., a l s o s u g g e s t no m a j o r b i a s i n f r e s h w a t e r l i f e h i s t o r y b e t w e e n t h e s e x e s ( S h e p h e r d e t a l . 1 9 8 6 b ) . From t h e s c a l e d a t a b a s e , t h e number o f i n d i v i d u a l s o c c u r r i n g i n e a c h age c l a s s f r o m 0.2 t o 3.6 was e n u m e r a t e d f r o m a minimum s a m p l e o f 50 a d u l t s p e r p o p u l a t i o n . The E u r o p e a n s y s t e m o f age d e s i g n a t i o n was u s e d ; t h e number t o t h e l e f t o f t h e d e c i m a l r e p r e s e n t s t h e number o f s c a l e a n n u l i f o r m e d i n f r e s h w a t e r a n d t h e number r i g h t o f t h e d e c i m a l r e p r e s e n t s t h e number o f m a r i n e a n n u l i . The mean p e r c e n t a g e s o f " s t r e a m - t y p e " (1 o r more f r e s h w a t e r a n n u l i ) a n d " o c e a n - t y p e " (no f r e s h w a t e r a n n u l u s ) l i f e h i s t o r i e s were c a l c u l a t e d f o r p o p u l a t i o n s f o r w h i c h m u l t i p l e y e a r s a m p l e s were a v a i l a b l e . T h e s e i n d i c a t o r s o f j u v e n i l e l i f e h i s t o r y were c h e c k e d when p o s s i b l e a g a i n s t f i e l d d a t a on m i g r a t i o n t i m i n g a n d s e a s o n a l a b u n d a n c e o f j u v e n i l e s i n f r e s h w a t e r . 120 G e o g r a p h i c d i s t r i b u t i o n o f c h i n o o k s a l m o n S p a w n i n g p o p u l a t i o n s o f c h i n o o k s a l m o n h a v e been r e c o r d e d i n t h e e a s t e r n P a c i f i c ( F i g . 16) f r o m a s f a r s o u t h a s t h e V e n t u r a R i v e r (34 d e g r e e s N l a t i t u d e ) i n s o u t h - c e n t r a l C a l i f o r n i a , t o P o i n t Hope, A l a s k a , a n d p e r h a p s e a s t t o t h e M a c K e n z i e a n d C o p p e r m i n e r i v e r s ( H a l l o c k a n d F r y 1967; M c P h a i l a n d L i n d s e y 1970; S c o t t a n d C r o s s m a n 1973; L e e e t a l . 1980; M c L e o d and M c N e i l 1 9 8 3 ) . I n f o r m a t i o n on t h e d i s t r i b u t i o n o f c h i n o o k p o p u l a t i o n s i n t h e w e s t e r n P a c i f i c i s f r a g m e n t a r y b u t p o p u l a t i o n s a p p e a r t o be l e s s a b u n d a n t a nd l e s s w i d e s p r e a d ( M a j o r e t a l . 1 9 7 8 ) . C h i n o o k s a l m o n o c c u r i n t h e A n a d y r R i v e r ( t r i b u t a r y t o t h e B e r i n g S e a ) , t h e K a m c h a t k a , B o l ' s h a y a a nd A v a c h a r i v e r s o f t h e K a m c h a t k a n P e n i n s u l a , t h e Amur R i v e r , a n d i n a few s t r e a m s t r i b u t a r y t o t h e Sea o f O k h o t s k a n d on n o r t h e r n H o k k a i d o ( B e r g 1948; S h m i d t 1950; H i k i t a 1956; V r o n s k i y 1 9 7 2 ) . W i t h i n t h i s b r o a d g e o g r a p h i c r a n g e c h i n o o k s a l m o n a r e d i s t r i b u t e d among a t l e a s t 1,000 s e p a r a t e s p a w n i n g p o p u l a t i o n s i n N o r t h A m e r i c a ( A r o a n d S h e p a r d 1967; A t k i n s o n e t a l . 1 9 6 7 ) . S p a w n i n g by a d u l t s a n d f r e s h w a t e r r e s i d e n c e by y o u n g s a l m o n o c c u r s i n a w i d e r a n g e o f d i f f e r e n t t y p e s o f r i v e r s , f r o m s m a l l c o a s t a l s t r e a m s o n l y a few k i l o m e t e r s f r o m t h e o c e a n t o l a r g e r i v e r s y s t e m s s u c h a s t h e S a c r a m e n t o - S a n J o a q u i n , C o l u m b i a , F r a s e r , a n d Y u k o n r i v e r s i n w h i c h h e a d w a t e r p o p u l a t i o n s may spawn up t o 3,200 km f r o m t h e s e a . H i s t o r i c a l l y , t h e C o l u m b i a R i v e r , w i t h i t s t r i b u t a r i e s i n O r e g o n , W a s h i n g t o n , I d a h o , a n d 121 F i g u r e 16. G e o g r a p h i c d i s t r i b u t i o n o f c h i n o o k s a l m o n i n t h e N o r t h P a c i f i c O c e a n . (1) S a c r a m e n t o - S a n J o a q u i n R. f (2) Snake R., (3) C o l u m b i a R., (4) F r a s e r R., (5) S k e e n a R., (6) Y u k o n R., (7) M a c k e n z i e R., (8) C o p p e r m i n e R., (9) P o i n t Hope, (10) A n a d y r R., (11) K a m c h a t k a R., ( 1 2 ) Amur R., ( 1 3 ) H o k k a i d o . 123 B r i t i s h C o l u m b i a , was p r o b a b l y t h e s i n g l e l a r g e s t p r o d u c e r o f c h i n o o k s a l m o n w i t h t o t a l s p a w n i n g r u n s o f o v e r 4,000,000 a d u l t s (Chapman 1 9 8 6 ) . R e c e n t l y , h o w e v e r , o v e r e x p l o i t a t i o n , dam c o n s t r u c t i o n , w a t e r a b s t r a c t i o n , a n d o t h e r f o r m s o f h a b i t a t a l t e r a t i o n h a v e g r e a t l y r e d u c e d t h e d o m i n a n c e o f t h e C o l u m b i a a s a p r o d u c e r o f w i l d c h i n o o k (Van H y n i n g 1973; Chapman 1 9 8 6 ) . C h i n o o k s a l m o n h a v e been i n t r o d u c e d t o s e v e r a l a r e a s o u t s i d e t h e i r n a t i v e r a n g e . I n t r o d u c t i o n s t o New Z e a l a n d s t r e a m s , s t a r t i n g i n t h e l a t e 1 8 0 0 ' s , h a v e been t h e most i m p o r t a n t a n d s u c c e s s f u l ( S t o k e l l 1962; R i c k e r 1 9 7 2 ) . A f t e r i n i t i a l l y s p o r a d i c r e s u l t s , s e l f - s u s t a i n i n g p o p u l a t i o n s o f v a r i a b l e s i z e h ave become e s t a b l i s h e d i n many New Z e a l a n d s t r e a m s on b o t h t h e e a s t a n d w e s t c o a s t s ( F l a i n 1972, 1 9 8 1 ) . O t h e r n o t a b l e i n t r o d u c t i o n s i n c l u d e t r a n s p l a n t s o f c h i n o o k t o s e v e r a l t r i b u t a r i e s o f t h e G r e a t L a k e s i n e a s t e r n N o r t h A m e r i c a a n d t o S o u t h e r n C h i l e ( L e e e t a l . 1980; C a r l 1982; F l a i n 1 9 8 3 ) . 1 24 G e o g r a p h i c v a r i a t i o n i n j u v e n i l e l i f e h i s t o r y S a c r a m e n t o - S a n J o a q u i n R i v e r a n d K l a m a t h R i v e r H i s t o r i c a l l y , s p a w n i n g p o p u l a t i o n s o f c h i n o o k s a l m o n were p r e s e n t up t o t h e h e a d w a t e r s o f b o t h t h e S a c r a m e n t o a nd San J o a q u i n r i v e r s i n C a l i f o r n i a ' s C e n t r a l V a l l e y ( C l a r k 1 9 2 9 ) . A t l e a s t 8 0 % o f t h e n a t u r a l s p a w n i n g a n d r e a r i n g a r e a i n t h e s e s y s t e m s h a s been e l i m i n a t e d by dam c o n s t r u c t i o n a n d w a t e r a b s t r a c t i o n . The S h a s t a a nd K e s w i c k dams n e a r R e d d i n g , C a l i f o r n i a , ( F i g . 17) were p e r h a p s t h e most d a m a g i n g ; a l l s a l m o n r u n s u p s t r e a m o f t h e s e b a r r i e r s w e r e e l i m i n a t e d (Needham e t a l . 1940; M o f f e t t 1 9 4 9 ) . M o s t o f t h e s e dams were c o n s t r u c t e d b e f o r e a n y d e t a i l e d s t u d i e s o f j u v e n i l e l i f e h i s t o r i e s were c o m p l e t e d f o r s p e c i f i c t r i b u t a r y p o p u l a t i o n s o f t h e S a c r a m e n t o -San J o a q u i n r i v e r s y s t e m . N e v e r t h e l e s s , much o f o u r p r e s e n t a p p r e c i a t i o n o f t h e d e g r e e o f v a r i a b i l i t y i n j u v e n i l e f r e s h w a t e r l i f e h i s t o r i e s i s d e r i v e d f r o m t h e e a r l y work o f S c o f i e l d ( 1 9 0 0 ) , R u t t e r ( 1 9 0 3 ) , R i c h ( 1 9 2 0 ) , a n d C l a r k ( 1 9 2 9 ) on S a c r a m e n t o R i v e r c h i n o o k s a l m o n . What i s c l e a r f r o m t h e s e e a r l y s t u d i e s i s t h a t b o t h s t r e a m - a n d o c e a n - t y p e j u v e n i l e l i f e h i s t o r i e s were p r e s e n t ( R i c h 1 9 2 0 ) , b u t t h e p r o p o r t i o n s o f o c e a n - o r s t r e a m - t y p e l i f e h i s t o r i e s i n s p e c i f i c t r i b u t a r i e s i s unknown. C l a r k ( 1 9 2 9 ) e x a m i n e d s c a l e s f r o m a d u l t c h i n o o k c o l l e c t e d n e a r t h e c o n f l u e n c e o f t h e S a c r a m e n t o a n d San J o a q u i n r i v e r s f o r 1 25 1919 a n d 1921; t h e p e r c e n t a g e o f s t r e a m - t y p e l i f e h i s t o r i e s i n t h e s c a l e s a m p l e s was between 9 and 13%. A p p a r e n t l y , most s t r e a m - t y p e f i s h were f r o m t h e h e a d w a t e r t r i b u t a r i e s ( R i c h 1920; C l a r k 1929; M a j o r e t a l . 1 9 7 8 ) . B e c a u s e dam c o n s t r u c t i o n h a s been c o n c e n t r a t e d i n u p s t r e a m r e a c h e s o f t h e S a c r a m e n t o , s t r e a m -t y p e p o p u l a t i o n s have p r o b a b l y been r e d u c e d more t h a n o c e a n -t y p e . A t p r e s e n t , t h e S a c r a m e n t o c o n t a i n s remnant p o p u l a t i o n s o f f o u r s e a s o n a l s p a w n i n g r u n s o f a d u l t c h i n o o k s a l m o n : f a l l , l a t e -f a l l , w i n t e r , a n d s p r i n g ( R i c k e r 1972; K j e l s o n e t a l . 1 9 8 2 ) . As t h e i r names s u g g e s t , t h e s e r u n s a r e d i s t i n g u i s h e d by t h e s e a s o n d u r i n g w h i c h a d u l t s a l m o n m i g r a t e u p s t r e a m . The f a l l r u n i s d o m i n a n t i n b o t h t h e S a c r a m e n t o a n d Sah J o a q u i n r i v e r s , c o n s t i t u t i n g a b o u t 80 a n d 100% o f t h e i r r e s p e c t i v e s p a w n i n g r u n s . W i t h i n t h e S a c r a m e n t o , most f a l l r u n c h i n o o k spawn i n m a i n s t e m a r e a s d o w n s t r e a m f r o m K e s w i c k Dam. T h e s e s a l m o n p r o d u c e p r e d o m i n a t e l y o c e a n - t y p e j u v e n i l e s t h a t b e g i n e n t e r i n g t h e d e l t a a r e a a s e a r l y a s D e c e m b e r - J a n u a r y a f t e r t h e a d u l t s h a v e spawned i n O c t o b e r - D e c e m b e r ( F r a n k F i s h e r , C a l i f o r n i a D e p t . F i s h a n d Game, S t o c k t o n , CA, p e r s . comm.; K j e l s o n e t a l . 1 9 8 2 ) . F r y a r e a b u n d a n t i n t h e d e l t a f r o m J a n u a r y t o M a r c h and m a r k e d f r y r e m a i n i n t h e e s t u a r y f o r r o u g h l y 2 months b e f o r e m i g r a t i n g o f f s h o r e ( K j e l s o n e t a l . 1 9 8 2 ) . The K l a m a t h R i v e r i n n o r t h e r n C a l i f o r n i a ( F i g . 17) i s a l s o a m a j o r p r o d u c e r o f c h i n o o k s a l m o n a n d s p a w n i n g p o p u l a t i o n s a r e 126 F i g u r e 17. D i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r i e s f o r c h i n o o k s a l m o n s p a w n i n g p o p u l a t i o n s i n t h e S a c r a m e n t o a n d K l a m a t h r i v e r s , C a l i f o r n i a . Open c i r c l e s : o c e a n - t y p e (> 7 5 % ) . (1) San J o a q u i n R., ( 2 ) S a c r a m e n t o R i v e r , (3) S o u t h F o r k T r i n i t y R. ( K l a m a t h R . ) , (4) Salmon R., (5) S c o t t R., (6) S h a s t a R., (7) Bogus C r . L a r g e s t a r = S a c r a m e n t o , s m a l l s t a r = S a n F r a n c i s c o . PACIFIC OCEAN 128 e i t h e r s p r i n g o r m i d - l a t e summer r u n ( S n y d e r 1931; R i c k e r 1 9 7 2 ) . M o s t j u v e n i l e s a l m o n i n t h e K l a m a t h s y s t e m a r e o c e a n - t y p e ; o n l y a b o u t 13% o f s p a w n i n g a d u l t s h a v e - s t r e a m - t y p e s c a l e s ( S y n d e r 1 9 3 1 ) . More r e c e n t e v i d e n c e , f r o m s c a l e s o f a d u l t s s p a w n i n g i n t r i b u t a r i e s o f t h e K l a m a t h , s u g g e s t t h a t t h e r e l a t i v e c o n t r i b u t i o n o f s t r e a m - t y p e l i f e h i s t o r i e s i s b e t w e e n 0 and 7% ( F i g 18, C a l i f . D e p t . o f F i s h a n d Game, u n p u b l . d a t a ) . A p p a r e n t l y , m i g r a n t c h i n o o k e n t e r t h e K l a m a t h e s t u a r y a f t e r a few months o f s t r e a m r e s i d e n c e b e c a u s e j u v e n i l e s were d e t e c t e d t h e r e o n l y d u r i n g " l a t e summer" ( S n y d e r 1 9 3 1 ) . O r e g o n c o a s t a l s y s t e m s S p a w n i n g p o p u l a t i o n s o f c h i n o o k . s a l m o n o c c u r t h r o u g h o u t P a c i f i c c o a s t a l O r e g o n and h a v e been t h e s u b j e c t o f numerous s t u d i e s o f j u v e n i l e l i f e h i s t o r y ( R e i m e r s 1968, 1973, 1979; S c h l u c h t e r a n d L i c h a t o w i c h 1977; N e i l s o n e t a l . 1985; N e i l s o n a n d Geen 1986; N i c h o l a s and H a n k i n 1 9 8 8 ) . R e c e n t l y , N i c h o l a s a n d H a n k i n ( 1 9 8 8 ) s u m m a r i z e d t h e p r e s e n t k n o w l e d g e o f v a r i a t i o n i n j u v e n i l e l i f e h i s t o r y f o r most m a j o r s t r e a m s o f t h e O r e g o n c o a s t e x c e p t t h e C o l u m b i a R i v e r a n d i t s t r i b u t a r i e s ( s e e b e l o w ) . B o t h f r o m s t r e a m s u r v e y s f o r j u v e n i l e s a nd f r o m s c a l e a n a l y s i s o f a d u l t s , i n some c a s e s o v e r a number o f y e a r s , i t i s c l e a r t h a t o c e a n - t y p e c h i n o o k p r e d o m i n a t e i n c o a s t a l O r e g o n s t r e a m s ( F i g . 18, N i c h o l a s a n d H a n k i n 1 9 8 8 ) . The p e r c e n t a g e o f s t r e a m -t y p e l i f e h i s t o r i e s e x c e e d e d 10% i n o n l y one o f 13 s t r e a m s f o r w h i c h d a t a were a v a i l a b l e ( N o r t h Umpqua). F o r a t l e a s t one 129 F i g u r e 18. D i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r y p a t t e r n s f o r c h i n o o k s a l m o n s p a w n i n g p o p u l a t i o n s i n O r e g o n c o a s t a l s t r e a m s . Open c i r c l e s : o c e a n - t y p e (> 7 5 % ) ; h a l f - c i r c l e s : i n t e r m e d i a t e (<75% o c e a n - o r s t r e a m - t y p e ) . (1) C h e t c o C r . , (2) H u n t e r C r . , (3) E l k R., (4) S i x e s R., (5) C o q u i l l e R., (6) Coos R., (7) Rogue R., (8) N o r t h Umpqua R., (9) S i u s l a w R., (10) Y a q u i n a R., (11) S i l e t z R., (12) S a lmon R., (13) N e s t u c c a R., (14) T r a s k R., ( 1 5 ) W i l s o n R., (16) N e h a l e m R. 130 131 s t r e a m ( E l k R i v e r ) t h e r e may h a v e b e e n a d e c l i n e i n t h e r e l a t i v e o c c u r r e n c e o f s t r e a m - t y p e l i f e h i s t o r y p a t t e r n s i n t h e s c a l e s o f a d u l t s o v e r t h e 17 y e a r p e r i o d f r o m 1968 t o 1985 ( N i c h o l a s and H a n k i n 1 9 8 8 ) . T h r o u g h o u t c o a s t a l O r e g o n , j u v e n i l e c h i n o o k a p p e a r i n e s t u a r i n e a r e a s i n l a t e s p r i n g ( M a y - J u n e ) , w h i c h i s somewhat l a t e r t h a n i n t h e S a c r a m e n t o - S a n J o a q u i n , and r e s i d e t h e r e f o r p e r i o d s o f up t o 5 months b e f o r e m i g r a t i n g t o w a t e r s o f h i g h e r s a l i n i t y ( N i c h o l a s and H a n k i n 1 9 8 8 ) . The t r e n d , t h e n , i s f o r s t r e a m r e s i d e n c e d u r i n g t h e e a r l y s p r i n g f o l l o w e d by e s t u a r i n e r e s i d e n c e d u r i n g t h e l a t e s p r i n g a n d summer. M o s t o c e a n - t y p e c h i n o o k h a v e e n t e r e d medium t o h i g h s a l i n i t y e s t u a r i n e a r e a s by S e p t e m b e r - O c t o b e r ( N i c h o l a s a n d H a n k i n 1 9 8 8 ) . More d e t a i l e d s c a l e s t u d i e s a r e c o n s i s t e n t w i t h t h e s e g e n e r a l i t i e s . B o t h R e i m e r s ( 1 9 7 3 ) a n d S c h l u c h t e r and L i c h a t o w i c h ( 1 9 7 3 ) c o n c l u d e d t h a t o f 5 t o 7 s c a l e p a t t e r n s o b s e r v e d i n a d u l t s r e t u r n i n g t o t h e S i x e s a n d Rogue r i v e r s , t h e m a j o r i t y were f i s h t h a t , a s j u v e n i l e s , h a d i n i t i a l l y r e s i d e d i n t h e r i v e r , b u t a s u n d e r y e a r l i n g s h a d s p e n t an e x t e n d e d p e r i o d i n e s t u a r i e s . C o l u m b i a R i v e r The C o l u m b i a R i v e r s y s t e m , c o v e r i n g a d r a i n a g e a r e a o f a b o u t 671,000 s q km ( M c P h a i l a n d L i n d s e y 1986, F i g . 1 9 ) , c o n s t i t u t e s numerous l a r g e a n d s m a l l t r i b u t a r i e s w h i c h s u p p o r t l o c a l s p a w n i n g a n d j u v e n i l e p o p u l a t i o n s o f c h i n o o k s a l m o n 132 g u r e 19. D i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r y p a t t e r n s f o r c h i n o o k s a l m o n s p a w n i n g p o p u l a t i o n s o f t h e C o l u m b i a R i v e r . Open c i r c l e s : o c e a n - t y p e (> 7 5 % ) ; c l o s e d c i r c l e s ; s t r e a m -t y p e ( > 7 5 % ) . (1) Upper W i l l a m e t t e R., (2) l o w e r W i l l a m e t t e R., (3) u p p e r D e s c h u t e s R., (4) l o w e r D e s c h u t e s R., (5) J o h n Day R., (6) T u c a n n o n R., (7) G r a n d e Ronde R., (8) Imnaha R., (9) L i t t l e S a l mon R., ( 1 0 ) S o u t h F o r k Salmon R., (11) B e a r V a l l e y C r . , ( 1 2 ) M a r s h C r . , ( 1 3 ) M i d d l e F o r k S almon R., ( 1 4 ) U p p e r Salmon R., (15) E a s t F o r k S a l m o n R., ( 1 6 ) . L e m h i R., (17) Y a k i m a R., ( 1 8 ) W e n a t c h e e R., (19) G r a y ' s R., (20) E l o c h o m a n R., ( 2 1 ) K l a t s k a n i e R., ( 2 2 ) Methhow R., ( 2 3 ) l o w e r W e n a t c h e e R., (24) K l i c k i t a t R., (25) W a s h o u g a l R., ( 2 6 ) G r a y ' s H a r b o u r , (27) C o w l i t z R. 134 ( F u l t o n 1 9 6 8 ) . P r o c e e d i n g u p s t r e a m f r o m t h e mouth o f t h e C o l u m b i a t h e m a j o r t r i b u t a r i e s a r e : t h e W i l l a m e t t e , D e s c h u t e s , J o h n Day, Y a k i m a , and W e n a t c h e e r i v e r s , a n d t h e C l e a r w a t e r and S almon r i v e r s y s t e m s o f t h e Snake R i v e r s u b d r a i n a g e . H i s t o r i c a l l y , c h i n o o k s a l m o n were p r e s e n t i n t h e h e a d w a t e r a r e a s o f t h e C o l u m b i a s y s t e m i n s o u t h e a s t e r n B.C., a n d t o a b o u t S h o s h o n e F a l l s i n s o u t h c e n t r a l I d a h o ( B r y a n t a n d P a r k h u r s t 1950; F u l t o n 1 9 6 8 ) . Dam c o n s t r u c t i o n a t G r a n d C o u l e e on t h e m a i n s t e m C o l u m b i a ( G r a n d C o u l e e Dam) and a t H e l l ' s C a n y on on t h e Snake R i v e r h a s e x t i r p a t e d p o p u l a t i o n s a b o v e t h e s e o b s t r u c t i o n s ( F i g . 1 9 ) , b u t w i l d s p a w n i n g p o p u l a t i o n s p e r s i s t i n s e v e r a l t r i b u t a r i e s o f t h e u p p e r Salmon R i v e r d r a i n a g e i n c e n t r a l a n d s o u t h c e n t r a l I d a h o . H i s t o r i c a l t r e a t m e n t s o f t h e j u v e n i l e l i f e h i s t o r y p a t t e r n s o f c h i n o o k s a l m o n i n c l u d e t h e work o f R i c h ( 1 9 2 0 ) , R i c h a n d Holmes ( 1 9 2 8 ) , a n d R e i m e r s a n d L o e f f e l ( 1 9 6 7 ) . J u v e n i l e l i f e h i s t o r i e s ( F i g . 19) e x t e n d f r o m m i g r a t i o n d o w n s t r e a m a s n e w l y - e m e r g e d f r y o r y o u n g p a r r ( e . g . t h e K l a s k a n i e R i v e r ( R e i m e r s amd L o e f f e l 1 9 6 7 ) ) t o y e a r l i n g m i g r a n t s ( e . g . T o u t l e R i v e r , Y a k i m a R i v e r , S a lmon R i v e r t r i b u t a r i e s , ( M a j o r and M i g h e l l 1969; R e i m e r s a n d L o e f f e l 1967; H o w e l l e t a l . 1 9 8 5 ) ) . Many t r i b u t a r i e s o f t h e C o l u m b i a R i v e r i l l u s t r a t e w i t h i n -s t r e a m v a r i a b i l i t y i n c h i n o o k l i f e h i s t o r y . A l t e r n a t i v e j u v e n i l e l i f e h i s t o r i e s w i t h i n s t r e a m s a r e u s u a l l y a s s o c i a t e d w i t h a d u l t s a l m o n r u n s t h a t e n t e r f r e s h w a t e r d u r i n g d i f f e r e n t 135 t i m e s a n d spawn i n d i f f e r e n t a r e a s . F o r e x a m p l e , t h e W i l l a m e t t e R i v e r i n t h e l o w e r C o l u m b i a , h a s b o t h s p r i n g a n d f a l l c h i n o o k r u n s . The s p r i n g r u n s a l m o n t y p i c a l l y spawn i n t h e u p p e r t r i b u t a r i e s s u c h as t h e M a c K e n z i e R i v e r ( r i v e r km 180) and h a v e a s t r e a m - t y p e j u v e n i l e l i f e h i s t o r y ( H o w e l l e t a l . 1 9 8 5 ) . I n c o n t r a s t , most f a l l r u n a d u l t s spawn i n s t r e a m s t r i b u t a r y t o t h e l o w e r W i l l a m e t t e ( l o w e r 40 km) a n d t h e i r p r o g e n y e m i g r a t e f r o m f r e s h w a t e r a s f r y ( H o w e l l e t a l . 1 9 8 5 ) . The p r e s e n c e o f b o t h l i f e h i s t o r y t y p e s w i t h i n s i n g l e t r i b u t a r i e s a p p e a r s t o be common i n t h e l o w e r C o l u m b i a R i v e r ( b e l o w i t s c o n f l u e n c e w i t h t h e S n a k e R i v e r ) ( F u l t o n 1 9 6 8 ) . T h e r e f o r e , t h e C o l u m b i a , b o t h h i s t o r i c a l l y a n d t o t h e p r e s e n t d a y , e x h i b i t s a r a n g e o f j u v e n i l e l i f e h i s t o r i e s b o t h among a n d w i t h i n component t r i b u t a r y s t r e a m s . O c e a n - t y p e m i g r a n t s e n t e r t h e C o l u m b i a e s t u a r y a s e a r l y a s December o f t h e y e a r o f s p a w n i n g b u t a r e most a b u n d a n t i n t h e e a r l y s p r i n g ( M a r c h - A p r i l ) . Some j u v e n i l e s e m i g r a t e f r o m c o a s t a l t r i b u t a r i e s a f t e r r e s i d i n g i n t h e i r n a t a l s t r e a m s t h r o u g h s p r i n g a n d summer a n d a p p e a r a s a s e c o n d a r y peak movement i n t o t h e e s t u a r y i n t h e l a t e f a l l ( e . g . R e i m e r s a n d L o e f f e l 1 9 6 7 ) . S t r e a m - t y p e c h i n o o k u s u a l l y m i g r a t e i n A p r i l t h r o u g h J u n e ( M a j o r a n d M i g h e l l 1969; H o w e l l e t a l . 1985) a l t h o u g h t h e y h a v e been f o u n d i n t h e e s t u a r y f r o m M a r c h t h r o u g h May ( R i c h 1920; McCabe e t a l . 1 9 8 3 ) . Once i n t h e C o l u m b i a e s t u a r y , s t r e a m - t y p e c h i n o o k a p p e a r t o s p e n d l i t t l e t i m e t h e r e b e f o r e m i g r a t i n g o f f s h o r e c o m p a r e d t o o c e a n - t y p e c h i n o o k s 136 (McCabe e t a l . 1 9 8 3 ) . W a s h i n g t o n c o a s t a l a n d P u g e t Sound c h i n o o k C h i n o o k s a l m o n p o p u l a t i o n s i n P u g e t Sound a n d c o a s t a l W a s h i n g t o n a r e d o m i n a t e d by o c e a n - t y p e j u v e n i l e l i f e h i s t o r y p a t t e r n s ( F i g . 2 0 ) . M o s t s y s t e m s , p a r t i c u l a r l y t h o s e on t h e w e s t c o a s t , a r e c h a r a c t e r i z e d by >95% o c e a n - t y p e c h i n o o k . I n a few o f t h e l a r g e r s y s t e m s t h a t h a v e t r i b u t a r i e s e x t e n d i n g i n t o t h e C a s c a d e M o u n t a i n s , s t r e a m - t y p e c h i n o o k a r e more a b u n d a n t ( e . g . S k a g i t a n d S n o h o m i s h r i v e r s a r e a b o u t 7 0% s t r e a m - t y p e ) . B o t h j u v e n i l e o c e a n - a n d s t r e a m - t y p e c h i n o o k e n t e r W a s h i n g t o n e s t u a r i e s f r o m M a r c h t h r o u g h J u n e , b u t o c e a n - t y p e m i g r a n t s p r e d o m i n a t e d u r i n g t h e e a r l y s p r i n g . A s e c o n d a r y peak o f m i g r a t i o n may o c c u r i n A u g u s t a n d S e p t e m b e r ( S i m e n s t a d e t a l . 1 9 8 2 ) . I n d i v i d u a l r e s i d e n c e t i m e s a v e r a g e 3-6 weeks i n W a s h i n g t o n e s t u a r i e s , b u t i n some s a l t m a r s h e s r e s i d e n c e may be o n l y a few d a y s ( C o n g l e t o n e t a l . 1982; S i m e n s t a d e t a l . 1 9 8 2 ) . B r i t i s h C o l u m b i a S o u t h e r n B r i t i s h C o l u m b i a ( V a n c o u v e r I s l a n d , S o u t h w e s t e r n M a i n l a n d , a n d F r a s e r R i v e r ) e x h i b i t s t h e f u l l r a n g e o f j u v e n i l e c h i n o o k l i f e h i s t o r y p a t t e r n s p r e s e n t i n more s o u t h e r n a r e a s ( F i g . 2 1 ) . V a n c o u v e r I s l a n d p o p u l a t i o n s a r e d o m i n a t e d by o c e a n -t y p e s a l m o n , b u t c e r t a i n p o p u l a t i o n s i l l u s t r a t e v a r i a b i l i t y t h a t 137 F i g u r e 20. D i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r y p a t t e r n s f o r c h i n o o k s a l m o n s p a w n i n g p o p u l a t i o n s o f c o a s t a l W a s h i n g t o n a n d P u g e t Sound. Open c i r c l e s : o c e a n - t y p e (> 7 5 % ) ; h a l f -c i r c l e s : i n t e r m e d i a t e (<75% s t r e a m - o r o c e a n - t y p e ) . (1) N o r t h F o r k N o o k s a c k R., (2) S o u t h F o r k N o o k s a c k R., (3) l o w e r N o o k s a c k R., (4) l o w e r S k a g i t R., (5) l o w e r Sauk R., (6) u p p e r S k a g i t R., (7) N o r t h F o r k S t i l l i g u a m i s h R., (8) S o u t h F o r k S t i l l i g u a m i s h R., (9) C e d a r R., ( 1 0 ) G r e e n R., (11) S k y k o m i s h R., (12) S n o q u a l m i e R., ( 1 3 ) P u y a l l u p R., (14) N i s q u a l l y R., ( 1 5 ) S k o k o m i s h R., ( 1 6 ) Hamma Hamma R., (17) D u c k a b u s h R., (18) D o s e w a l l i p s R., ( 1 9 ) D u n g e n e s s R., (21) E l w h a R., (22 ) Hoko R., ( 2 3 ) Q u i l l a y u t e R., (24) Hoh R., (25 ) C l e a r w a t e r R., (26) Q u e e t s R., (27 ) Q u i n a u l t R., (28) H u m p t u l i p s R., (29) C h e h a l i s R., ( 3 0 ) W i l l a p a R., (31) u p p e r Sauk R. S t a r = S e a t t l e . 139 F i g u r e 2 1 . D i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r y p a t t e r n s i n c h i n o o k s a l m o n s p a w n i n g p o p u l a t i o n s i n s o u t h e r n B r i t i s h C o l u m b i a . Open c i r c l e s : o c e a n - t y p e (> 7 5 % ) ; c l o s e d c i r c l e s : s t r e a m - t y p e ( > 7 5 % ) ; h a l f - c i r c l e s : i n t e r m e d i a t e . . (1) N i t i n a t R., (2) G o r d o n R., (3) San J u a n R., (4) C o w i c h a n R., (5) Nanaimo R., (6) A l b e r n i I n l e t , ( 7 ) B i g Q u a l i c u m R., (8) L i t t l e Q u a l i c u m R., (9) P u n t l e d g e R., (10) G o l d R., (11) Burman R., (12) Q u i n s a m R., ( 1 3 ) C a m p b e l l R., (14) Conuma R., (15) S almon R., (16) Woss R., ( 1 7 ) M a r b l e R., (18) A s h l u R., (19) S q u a m i s h R., ( 2 0 ) H a r r i s o n R., (21) B i r k e n h e a d R., (22) C o l d w a t e r R., ( 2 3 ) N i c o l a R., (24) Adams R., ( 2 5 ) S o u t h Thompson R., ( 2 6 ) S a l m o n R., (27) Shuswap R., ( 2 8 ) E a g l e R., (29) Deadman R., ( 3 0 ) C l e a r w a t e r R., ( 3 1 ) B l u e R., ( 3 2 ) N o r t h Thompson R., ( 3 3 ) C h i l k o R., ( 3 4 ) C h i l c o t i n R., ( 3 5 ) H o r s e f l y R., (36) M c K i n l e y C r . , ( 3 7 ) Q u e s n e l R., ( 3 8 ) Bowron R., ( 3 9 ) S l i m C r . , (40) S w i f t C r . , ( 4 1 ) T e t e J e a n ( F r a s e r R . ) , (42) H olmes R., (43) W a l k e r C r . , ( 4 4 ) M c G r e g o r R., ( 4 5 ) W i l l o w R., ( 4 6 ) Salmon R., ( 4 7 ) S t u a r t R., ( 4 8 ) N e c h a k o R., (49) A h n u h a t i R., ( 5 0 ) M u s s e l C r . , (51) Wannock R., ( 5 2 ) K i l b e l l a R., (53) B e l l a C o o l a R., ( 5 4 ) A t n a r k o R., ( 5 5 ) H i r s c h C r . , (56) K i l d a t a R., (57) K i t i m a t R., ( 5 8 ) M o r i c e R., ( 5 9 ) Zymoetz R., ( 6 0 ) K i t s u m k a l u m R., ( 6 1 ) E c k s t a l l R., ( 6 2 ) Yakoun R., ( 6 3 ) K i s p i o x R., ( 6 4 ) B a b i n e R., (65) B e a r R., (67) K i n c o l i t h R., ( 6 8 ) C r a n b e r r y R., (69) M e z i a d i n R., (70) C h i c k a m i n R., (71) Unuk R., ( 7 2 ) B r a d f i e l d C a n a l . S t a r = V a n c o u v e r . 140 141 may e x i s t w i t h i n s i n g l e , r e a s o n a b l y s m a l l r i v e r systems. For example, the c h i n o o k i n the Nanaimo R i v e r on s o u t h e a s t e r n Vancouver I s l a n d a r e p r e d o m i n a t e l y (>95%) ocean-type, but t h e r e i s a s m a l l p o p u l a t i o n of up t o 50% stream-type i n d i v i d u a l s i n the headwaters ( C a r l and Healey 1984). In a d d i t i o n , the ocean-type chinook m i g r a t e t o the e s t u a r y e i t h e r as f r y (lower r i v e r spawning p o p u l a t i o n ) or a f t e r 2-3 months of stream r e s i d e n c e ( m i d d l e r i v e r spawning p o p u l a t i o n ) ( C a r l and H e a l e y 1984). S i m i l a r l y , the B i g Qualicum R i v e r appears t o have d i s t i n c t newly-emerged and 2-3 month o l d ocean-type m i g r a n t s ( L i s t e r and Walker 1966; L i s t e r and Geno 1970). The F r a s e r R i v e r shows a predominance of the stream-type l i f e h i s t o r y i n terms of the number of p o p u l a t i o n s . The H a r r i s o n R i v e r , however, i s the s i n g l e l a r g e s t spawning p o p u l a t i o n w i t h i n the F r a s e r system (about 25% of mean annual F r a s e r escapement 1976-80, F r a s e r e t a l . 1982) and i s ocean-t y p e ; f r y e m i g r a t e t o the F r a s e r e s t u a r y d u r i n g March and A p r i l ( F r a s e r et a l . 1982; Levy and N o r t h c o t e 1982). N o r t h of about 50 degrees N l a t i t u d e , the F r a s e r i s dominated by stream-type p o p u l a t i o n s e xcept f o r some a p p a r e n t l y i n t e r m e d i a t e p o p u l a t i o n s i n the South Thompson s u b - d r a i n a g e ( F i g . 2 1 ) . Areas n o r t h t o the Nass R i v e r e x h i b i t an i n c r e a s i n g tendency towards d o m i n a t i o n by stream-type p o p u l a t i o n s w i t h n o t a b l e e x c e p t i o n s b e i n g the Whonnock, B e l l a C o o l a , and K i t i m a t R i v e r s on the c o a s t . N o r t h of the Nass R i v e r , the Canadian 142 p o r t i o n s o f t h e S t i k i n e a n d T a k u r i v e r s , a n d t h e i r t r i b u t a r i e s , a p p e a r t o h a v e e x c l u s i v e l y s t r e a m - t y p e p o p u l a t i o n s ( F i g . 2 2 ) . By c o n t r a s t t o s o u t h e r n a r e a s , e v e n s m a l l s t r e a m s c l o s e t o t h e c o a s t h a v e s t r e a m - t y p e c h i n o o k ( e . g . H a r d i n g R i v e r , s t r e a m s t r i b u t a r y t o Unuk R i v e r , F i g . 2 1 ) . I n s o u t h e r n B.C., o c e a n - t y p e c h i n o o k e n t e r e s t u a r i n e a r e a s a s n e w l y - e m e r g e d f r y a s e a r l y a s M a r c h and on t h r o u g h May ( L i s t e r a n d Genoe 1970; L e v y a n d N o r t h c o t e 1982; H e a l e y 1980, 1982; L e v i n g s e t a l . 1 9 8 6 ) . F o r some p o p u l a t i o n s , p e a k s i n d o w n s t r e a m movement may d i f f e r up t o 1 month f r o m y e a r t o y e a r ( L i s t e r a n d W a l k e r 1966; F r a s e r e t a l . 1 9 8 2 ) . F r y r e s i d e i n e s t u a r i n e a r e a s f o r b e t w e e n 4 a n d 8 weeks u n t i l t h e y r e a c h a s i z e o f b e t w e e n 2 a n d 4 g, a f t e r w h i c h t h e y m i g r a t e f a r t h e r o f f s h o r e ( H e a l e y 1980, 1982; L e v y a n d N o r t h c o t e 1982; L e v i n g s e t a l . 1 9 8 6 ) . J u v e n i l e c h i n o o k t h a t r e s i d e i n t h e i r n a t a l s t r e a m s f o r 2-3 months a f t e r e m e r g e n c e b e g i n e n t e r i n g e s t u a r i n e a r e a s f r o m May t o J u n e where t h e y may r e m a i n u n t i l J u l y - A u g u s t ( L i s t e r a n d W a l k e r 1966; H e a l e y 1980, 1982; F r a s e r e t a l . 1982; C a r l a n d H e a l e y 1984; S h e p h e r d e t a l . 1 9 8 6 a ) . S t r e a m - t y p e c h i n o o k m i g r a t e d o w n s t r e a m p r i m a r i l y i n A p r i l a n d May i n s o u t h and c e n t r a l B.C., w i t h p e a k s n e a r t h e e n d o f A p r i l , a n d e n t e r e s t u a r i n e a r e a s f r o m May t h r o u g h J u n e ( L e v y a n d L e v i n g s 1978; S h e p h e r d e t a l . 1 9 8 6 b ) . S e a w a r d m i g r a t i o n a p p e a r s t o be l a t e r f a r t h e r n o r t h where peak movement o c c u r s i n mid-May i n t h e T a k u a n d S t i k i n e r i v e r s . (Meehan a n d S n i f f 1962; 1 43 P. K i s s n e r , A l a s k a D e p t . o f F i s h a n d Game, p e r s . comm.). Once i n e s t u a r i n e a r e a s , s t r e a m - t y p e c h i n o o k a p p a r e n t l y s e e k t h e o u t e r m a r g i n s o f t h e s e h a b i t a t s a n d s p e n d l i t t l e t i m e t h e r e , c o m p a r e d t o o c e a n - t y p e c h i n o o k s , b e f o r e m i g r a t i n g t o w a r d s t h e open o c e a n ( L e v y a n d L e v i n g s 1978; H e a l e y 1 9 8 3 ) . A l a s k a a n d Yukon p o p u l a t i o n s The d i s t r i b u t i o n o f j u v e n i l e c h i n o o k l i f e h i s t o r y p a t t e r n s i s p e r h a p s l e a s t v a r i a b l e i n c o a s t a l a n d i n l a n d a r e a s i n A l a s k a , a n d i n Yukon p o r t i o n s o f t h e Yukon R i v e r , where a l l p o p u l a t i o n s s a m p l e d t o d a t e a r e s t r e a m - t y p e ( F i g . 2 2 ) . A l a s k a n a n d Yukon R i v e r s t r e a m - t y p e c h i n o o k may s p e n d up t o 2 y e a r s i n f r e s h w a t e r b e f o r e m i g r a t i n g s e a w a r d ( M c B r i d e a n d W i l c o c k 1983; M i l l i g a n e t a l . 1 9 8 5 ) . O n l y v e r y o c c a s i o n a l l y do o c e a n - t y p e l i f e h i s t o r i e s a p p e a r i n s c a l e s a m p l e s o f a d u l t s r e t u r n i n g t o spawn i n c e r t a i n c o a s t a l p o p u l a t i o n s i n s o u t h e a s t e r n a n d s o u t h w e s t e r n A l a s k a ( A l a s k a D e p t . F i s h a n d Game, u n p u b l . d a t a ) . S e a w a r d m i g r a t i o n o f A l a s k a n a n d Yukon R i v e r c h i n o o k s a l m o n i s g e n e r a l l y l a t e r t h a n i n more s o u t h e r n p o r t i o n s o f t h e C h i n o o k ' s r a n g e , e x t e n d i n g f r o m May t o l a t e J u l y ( W a l k e r 1976; L o f t u s a n d Le n o n 1977; Raymond 1981; M a r t i n e t a l . 1 9 8 7 ) . As i s c o n s i s t e n t w i t h e s t u a r i n e r e s i d e n c e d i s t r i b u t i o n o f s t r e a m - t y p e s a l m o n i n more s o u t h e r n l a t i t i d e s , Y u k on R i v e r c h i n o o k u t i l i z e t h e d e e p e r h a b i t a t s i n t h e p r o d e l t a b e f o r e m o v i n g o f f s h o r e ( M a r t i n e t a l . 1 9 8 7 ) . 144 u r e 22. D i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r y p a t t e r n s i n c h i n o o k s p a w n i n g p o p u l a t i o n s i n n o r t h e r n B.C. a n d A l a s k a . C l o s e d c i r c l e s : s t r e a m - t y p e ( > 7 5 % ) . (1) K w i n i u k R., (2) U n a l a k l e e t R., (3) A n d r e a f s k y R., (4) A n v i k R., (5) N u l a t o R., (6) Chena R., (7) S a l c h a R., (8) B i g Salmon R., (9) Yukon R. ( W h i t e h o r s e ) , ( 1 0 ) T e s l i n R., ( 1 1 ) S w i f t R., (12) N i s u t l i n R., (13) K u s k o k w i m R., (14) H o l i t n a R., ( 1 5 ) Naknek R., ( 1 6 ) K i n g S almon R., (17) K a r l u k R., ( 1 8 ) A n c h o r R., ( 1 9 ) L i t t l e S u s i t n a R., (20) M o n t a n a C r . ( S u s i t n a R . ) r (21) C h u l i t n a R., ( 2 2 ) C o p p e r R., (23) A l s e k R., ( 2 4 ) T a h i n i R., (25) N a k i n a R. ( T a k u R . ) , ( 2 6 ) N a h l i n R. ( T a k u R . ) , ( 2 7 ) T a h l t a n a nd L i t t l e T a h l t a n R. ( S t i k i n e R . ) , ( 2 8 ) H a r d i n g R. 146 W e s t e r n P a c i f i c a n d New Z e a l a n d p o p u l a t i o n s I n f o r m a t i o n on t h e d i s t r i b u t i o n o f j u v e n i l e c h i n o o k l i f e h i s t o r i e s i s l i m i t e d i n a r e a s o t h e r t h a n t h e e a s t e r n P a c i f i c . S c a l e a n a l y s i s o f s a l m o n c a u g h t i n t h e w e s t e r n P a c i f i c n e a r t h e K a m c h a t k a p e n i n s u l a and i n t h e Sea o f O k h o t s k , a n d p r e s u m a b l y o f A s i a n o r i g i n , were a l l s t r e a m - t y p e (Mason 1 9 6 5 ) . V r o n s k i y (1972) s a m p l e d s c a l e s f r o m a d u l t c h i n o o k r e t u r n i n g t o spawn i n t h e u p p e r K a m c h a t k a R i v e r ( F i g . 16) d u r i n g 1965-70; a l l were s t r e a m - t y p e a n d a b o u t 12% s p e n t 2 y e a r s i n f r e s h w a t e r ( T a b l e 21 ) . I n New Z e a l a n d , t h e R a k a i a R i v e r , a n d i t s component t r i b u t a r i e s , i s t h e most s t u d i e d s y s t e m ( F l a i n 1982a; U n w i n 1 9 8 6 ) . I n t h i s s y s t e m , o c e a n - t y p e c h i n o o k p r e d o m i n a t e ( T a b l e 2 1 ) ; most a d u l t s t h a t s u r v i v e t o spawn s p e n d 2-3 months r e s i d i n g i n f r e s h w a t e r a s j u v e n i l e s b e f o r e m i g r a t i n g s e a w a r d ( F l a i n 1982a; Unwin 1 9 8 6 ) . As i n t h e n o r t h e r n h e m i s p h e r e , s t r e a m - t y p e c h i n o o k t e n d t o become more numerous w i t h i n c r e a s i n g l a t i t u d e i n New Z e a l a n d ( T a b l e 2 1 ) . Whereas up t o 30% o f s a m p l e d a d u l t c h i n o o k were s t r e a m - t y p e i n t h e R a n g i t a t a R i v e r ( D a v i s e t a l . 1 9 8 6 ) , a b o u t 50% o f a d u l t s s a m p l e d i n t h e W a i t a k i R i v e r were s t r e a m - t y p e (James a n d D e v e r a l l 1 9 8 7 ) . More l i m i t e d s a m p l i n g s u g g e s t s t h a t a b o u t 50% o f t h e a d u l t s c a u g h t i n s e a f i s h e r i e s n e a r t h e M o e r a k i P e n i n s u l a were s t r e a m - t y p e f i s h ( F l a i n 1 9 8 1 ) . I n a few s y s t e m s , c h i n o o k may r e s i d e p e r m a n e n t l y i n f r e s h w a t e r 147 T a b l e 2 1 . J u v e n i l e c h i n o o k l i f e h i s t o r y p a t t e r n s i n t h e K a m c h a t k a R i v e r ( S o v i e t U n i o n ) and s e v e r a l New Z e a l a n d r i v e r s K a m c h a t k a n d a t a i s f r o m V r o n s k i y ( 1 9 7 2 ) ; New Z e a l a n d d a t a f r o m F l a i n ( 1 9 7 2 ) , Unwin ( 1 9 8 6 ) , D a v i e s e t a l . ( 1 9 8 6 ) , a n d James a n d D e v e r a l l ( 1 9 8 7 ) . R i v e r L a t i t u d e Y e a r s P e r c e n t S t r e a m - t y p e K a m c h a t k a R i v e r 55' 10 N 1965-70 100 G l e n a r i f f e S t r e a m 43' 28 S 1967-76 8-34 ( R a k a i a R i v e r ) R a n g i t a t a R i v e r W a i t a k i R i v e r M o e r a k i P e n i n s u l a 4 3 '35" 44'40" 45'20" S S s 1972-83 1976-83 1976 28 26-66 58 148 d e s p i t e a c c e s s t o t h e s e a ( F l a i n 1 9 7 2 ) . Some i n d i v i d u a l s i n t h e a nadromous c o m p o n e n t s o f t h e s e p o p u l a t i o n s may s p e n d 2 o r 3 y e a r s i n f r e s h w a t e r b e f o r e s e a w a r d m i g r a t i o n ( F l a i n 1 9 8 0 ) . I n t h e R a k a i a R i v e r , s e a w a r d m i g r a t i o n by o c e a n - t y p e f i s h o c c u r s p r i m a r i l y i n November t h r o u g h J a n u a r y f o l l o w i n g e m ergence i n S e p t e m b e r (Unwin 1 9 8 6 ) . The a d u l t s t h a t m i g r a t e d t o s e a a s y e a r l i n g s m o l t s ( a b o u t 23%) d i d so f r o m A u g u s t t h r o u g h November (Un w i n 1 9 8 6 ) . I n summary, t h e r e i s e x t e n s i v e v a r i a t i o n i n j u v e n i l e l i f e h i s t o r y b o t h w i t h i n a n d among t r i b u t a r y p o p u l a t i o n s o f c h i n o o k , b u t a few g e n e r a l i t i e s c a n be d r a w n . F i r s t , s t r e a m - t y p e c h i n o o k t e n d t o p r e d o m i n a t e w i t h i n c r e a s i n g l a t i t u d e , a l t h o u g h t h e t r a n s i t i o n i s n o t a smooth one. S e c o n d , i n r i v e r s y s t e m s w i t h l a r g e numbers o f p o p u l a t i o n s , s t r e a m - t y p e c h i n o o k s p r e d o m i n a t e i n i n t e r i o r a r e a s a n d o c e a n - t y p e s i n c o a s t a l a r e a s . L a s t l y , a l t e r n a t i v e j u v e n i l e l i f e h i s t o r i e s c a n be f o u n d i n s i n g l e t r i b u t a r i e s . S u c h s u b - p o p u l a t i o n s a r e u s u a l l y a s s o c i a t e d w i t h s e a s o n a l a d u l t s p a w n i n g r u n s a n d s t r e a m - t y p e c h i n o o k s t e n d t o p r e d o m i n a t e i n t h e h e a d w a t e r s o f s i n g l e t r i b u t a r i e s . 149 2. ENVIRONMENTAL CORRELATES OF VARIATION I N J U V E N I L E CHINOOK L I F E HISTORY M e t h o d s F o u r e n v i r o n m e n t a l v a r i a b l e s c h a r a c t e r i s t i c o f c h i n o o k s p a w n i n g s t r e a m s were e x a m i n e d f o r t h e i r c o v a r i a t i o n w i t h j u v e n i l e l i f e h i s t o r y : mean a n n u a l a i r t e m p e r a t u r e , h o u r s o f d a y l i g h t a t f i r s t f e e d i n g , t o t a l d a y l i g h t h o u r s d u r i n g t h e g r o w i n g s e a s o n , and f r e s h w a t e r m i g r a t i o n d i s t a n c e . T e m p e r a t u r e a nd p h o t o p e r i o d a r e m a j o r a b i o t i c f a c t o r s r e g u l a t i n g g r o w t h a nd g r o w t h r a t e - d e p e n d e n t p r o c e s s e s i n f i s h e s ( B r e t t 1979; T h o r p e 1987; Hoar 1 9 8 8 ) . Not o n l y i s g r o w t h e x p e c t e d t o i n c r e a s e r a p i d l y w i t h i n c r e a s i n g t e m p e r a t u r e w i t h i n l i m i t s ( e . g . B r e t t e t a l . 1 9 6 9 ) , b u t f e e d i n g a n d g r o w t h commence e a r l i e r i n d e v e l o p m e n t a s t e m p e r a t u r e i n c r e a s e s (Heming e t a l . 1 9 8 2 ) . T h o r p e e t a l . (1989) d e m o n s t r a t e d t h a t t e m p e r a t u r e and p h o t o p e r i o d were g o o d i n d i c e s o f " g r o w t h o p p o r t u n i t y " i n l a b o r a t o r y p o p u l a t i o n s o f j u v e n i l e A t l a n t i c s a l m o n . A c o m b i n a t i o n o f t h e s e v a r i a b l e s ( t h e " t h e r m a l sum i n d e x " ) was an e x c e l l e n t p r e d i c t o r o f t h e p e r c e n t a g e o f f i s h w i t h i n s i b l i n g p o p u l a t i o n s t h a t w o u l d s m o l t a t 1 r a t h e r t h a n 2 y e a r s o f age ( T h o r p e e t a l . 1 9 8 9 ) . T e m p e r a t u r e a n d p h o t o p e r i o d a l s o a p p e a r t o be m a j o r d e t e r m i n a n t s o f f r e s h w a t e r l i f e h i s t o r y v a r i a t i o n among w i l d p o p u l a t i o n s o f A t l a n t i c s a l m o n ( M e t c a l f e a n d T h o r p e 1 9 8 9 ) . 150 P h o t o p e r i o d c o n d i t i o n s e x p e r i e n c e d d u r i n g e a r l y r e a r i n g i n f l u e n c e t h e g r o w t h t r a j e c t o r i e s o f s t r e a m - t y p e c h i n o o k a n d j u v e n i l e c o h o s a l m o n ( C l a r k e a n d S h e l b o u r n e 1986; C l a r k e 1987; C l a r k e a n d W i t h l e r 1987; T h o r a r e n s e n a n d C l a r k e 1 9 8 9 ) . Salmon t h a t e x p e r i e n c e " l o w " d a y l i g h t (< 12 h r ) a t f i r s t f e e d i n g grow f a s t e r and d i s p l a y p h y s i o l o g i c a l c o r r e l a t e s o f s m o l t i n g e a r l i e r t h a n s l o w e r g r o w i n g j u v e n i l e s t h a t e x p e r i e n c e " l o n g " d a y l i g h t p e r i o d s a t f i r s t f e e d i n g . The d a t a o f Zaugg e t a l . ( 1 9 8 6 ) a l s o s u g g e s t t h a t p h o t o p e r i o d c o n d i t i o n s a t f i r s t f e e d i n g may, i n p a r t , i n f l u e n c e t h e r a t e a t w h i c h s i z e a n d p h y s i o l o g i c a l c o r r e l a t e s o f s m o l t i n g a r e a c h i e v e d i n c h i n o o k s a l m o n . S i n c e w i l d p o p u l a t i o n s o f j u v e n i l e c h i n o o k e x p e r i e n c e d i f f e r e n t p h o t o p e r i o d r e g i m e s a t f i r s t f e e d i n g due t o v a r i a t i o n i n l a t i t u d e a n d emergence t i m i n g , p h o t o p e r i o d a t f i r s t f e e d i n g may e x p l a i n some o f t h e v a r i a b i l i t y i n d u r a t i o n o f f r e s h w a t e r r e s i d e n c e among p o p u l a t i o n s . L a s t l y , l o n g e r s m o l t m i g r a t i o n s a r e p r o b a b l y more c o s t l y i n t e r m s o f e n e r g y e x p e n d i t u r e a n d e x p o s u r e t o f r e s h w a t e r p r e d a t o r s . I n c r e a s i n g m i g r a t i o n d i s t a n c e m i g h t , t h e r e f o r e , s e l e c t f o r i n c r e a s i n g s i z e a t m i g r a t i o n . S i z e a t m i g r a t i o n a n d g r o w t h o p p o r t u n i t y c o u l d i n t e r a c t t o i n f l u e n c e age a t m i g r a t i o n . F r e s h w a t e r age d i s t r i b u t i o n d a t a f o r c h i n o o k p o p u l a t i o n s w ere c o l l e c t e d o v e r a s w i d e a g e o g r a p h i c r a n g e a s p o s s i b l e s u c h t h a t v a r i a b i l i t y i n b o t h j u v e n i l e l i f e h i s t o r y a n d e n v i r o n m e n t a l 151 v a r i a b l e s was m a x i m i z e d . L i m i t e d d a t a , h o w e v e r , were a v a i l a b l e f o r a v e r a g e s t r e a m w a t e r t e m p e r a t u r e s a c r o s s a w i d e g e o g r a p h i c r a n g e . Whereas most o f t h e B.C. a n d Yukon chinook p o p u l a t i o n s h a d r e a s o n a b l e t i m e s e r i e s d a t a on w a t e r t e m p e r a t u r e s o f t h e i r s p a w n i n g s t r e a m s , s i m i l a r d a t a w e re n o t g e n e r a l l y a v a i l a b l e f o r s p a w n i n g s t r e a m s i n o t h e r p a r t s o f t h e r a n g e . T h e r e f o r e , a i r t e m p e r a t u r e a t c l i m a t i c s t a t i o n s i n c l o s e p r o x i m i t y t o t h e s t u d y s t r e a m s , f o r w h i c h more c o m p l e t e d a t a were a v a i l a b l e , was u s e d a s an i n d i c a t o r o f w a t e r t e m p e r a t u r e . The i m p l i c i t a s s u m p t i o n t h a t a i r t e m p e r a t u r e s a r e r e a s o n a b l e p r e d i c t o r s o f s t r e a m t e m p e r a t u r e s was t e s t e d by c o m p a r i n g t h e s e t e m p e r a t u r e s f o r 50 s t r e a m s f o r w h i c h b o t h s t a t i o n a i r t e m p e r a t u r e s and w a t e r t e m p e r a t u r e s were a v a i l a b l e . A i r t e m p e r a t u r e d a t a were f r o m Anon ( 1 9 8 2 ) , W e r n s t e d t ( 1 9 7 2 ) , a n d R u f f n e r ( 1 9 85) w h i l e w a t e r t e m p e r a t u r e s were t a k e n f r o m Anon ( 1 9 7 7 ) , Unwin ( 1 9 8 6 ) , a n d f r o m u n p u b l i s h e d d a t a o f t h e C a l i f o r n i a D e p a r t m e n t o f F i s h a n d Game ( F . F i s h e r , S t o c k t o n , CA, p e r s . comm.). B o t h a i r a n d w a t e r t e m p e r a t u r e d a t a were f r o m s t r e a m s r e p r e s e n t a t i v e o f most o f t h e Chinook's r a n g e ( C a l i f o r n i a t o A l a s k a ) , a l t h o u g h t h e m a j o r i t y o f d a t a were f r o m B.C. a n d Yukon s t r e a m s . A p p r o x i m a t e l y 70% o f t h e among s t r e a m v a r i a t i o n i n mean a n n u a l w a t e r t e m p e r a t u r e c o u l d be a c c o u n t e d f o r by v a r i a t i o n i n mean a n n u a l a i r t e m p e r a t u r e ( F i g . 23, d f = 1 , 4 9 ; P < 0 . 0 0 0 1 ) . Mean a n n u a l a i r t e m p e r a t u r e was, t h e r e f o r e , u s e d a s a r e a s o n a b l e c o r r e l a t e o f mean a n n u a l w a t e r t e m p e r a t u r e . Power ( 1 9 8 1 ) , L ' A b e e - L u n d e t a l . ( 1 9 8 9 ) , M e t c a l f e a n d T h o r p e ( 1 9 8 9 ) . A l l 1 52 F i g u r e 2 3 . R e l a t i o n s h i p b e t w e e n mean a n n u a l a i r t e m p e r a t u r e a n d mean a n n u a l w a t e r t e m p e r a t u r e f o r s t u d y s t r e a m s . MEAN WATER TEMPERATURE (degress C) ro *>- CT> Co O ro J L _ I I I I L I 00 esi 1 54 f o u n d a i r t e m p e r a t u r e , a s a m e a s u r e o f g r o w i n g s e a s o n l e n g t h , t o be a good p r e d i c t o r o f s m o l t i n g a g e s f o r A t l a n t i c s a l m o n a n d brown t r o u t ( S a l m o t r u t t a ) p o p u l a t i o n s . Even g i v e n p e r f e c t c o r r e l a t i o n b e t w e e n a i r a n d w a t e r t e m p e r a t u r e s , p e r h a p s t h e more c r i t i c a l a s s u m p t i o n i s t h a t m e a s u r e s o f mean w a t e r t e m p e r a t u r e f o r a s t r e a m a r e r e l a t e d t o t h e r m a l m i c r o h a b i t a t s o c c u p i e d by j u v e n i l e s . T h e r e a r e c e r t a i n l y c a s e s i n w h i c h w a t e r t e m p e r a t u r e m o n i t o r i n g s t a t i o n s a r e r e m o t e f r o m t h e mai n j u v e n i l e s a l m o n h a b i t a t i n a s t r e a m . T e m p e r a t u r e s t a t i o n s a n d j u v e n i l e h a b i t a t may, t h u s , h a v e d i f f e r e n t w a t e r t e m p e r a t u r e r e g i m e s o w i n g t o t h e i n f l u e n c e o f l o c a l c o n d i t i o n s s u c h a s l a k e o u t l e t s o r s o u r c e s o f g r o u n d w a t e r . U n f o r t u n a t e l y , d a t a on t h e r m a l m i c r o h a b i t a t s f o r a w i d e r a n g e o f s t r e a m s a r e n o t p r e s e n t l y a v a i l a b l e . L a t i t u d e s o f s t u d y s t r e a m s were d e t e r m i n e d f r o m t o p o g r a p h i c maps ( 1 : 5 0 0 , 0 0 0 ) a n d were t a k e n a t t h e m i d - l e n g t h p o i n t o f e a c h s t r e a m u n l e s s i n f o r m a t i o n on t h e s p a w n i n g d i s t r i b u t i o n o f a d u l t s a l m o n i n d i c a t e d a more r e s t r i c t e d d i s t r i b u t i o n . From l a t i t u d e s , mean m o n t h l y h o u r s o f d a y l i g h t were d e t e r m i n e d f o r e a c h s t r e a m u s i n g t h e methods o u t l i n e d i n D u f f e t t - S m i t h ( 1 9 8 5 ) . H o u r s o f d a y l i g h t on t h e m i d day o f t h e month t h a t mean o m o n t h l y a i r t e m p e r a t u r e e x c e e d e d 4 C was u s e d a s a m e a s u r e o f p h o t o p e r i o d d u r i n g e a r l y g r o w t h o f j u v e n i l e s a l m o n . A o . . . t e m p e r a t u r e o f 4 C was c h o s e n b e c a u s e g r o w t h o f j u v e n i l e c h i n o o k i s t e m p e r a t u r e d e p e n d e n t a n d j u v e n i l e s a l m o n i d s e x h i b i t r e d u c e d a c t i v i t y a n d " h i d i n g " b e h a v i o u r a t t e m p e r a t u r e s b e l o w a b o u t 4-155 5 C (Chapman a n d B j o r n n 1969; T a y l o r 1 9 8 8 ) . F e e d i n g a c t i v i t y i s o p r o b a b l y g r e a t l y r e d u c e d a t t e m p e r a t u r e s b e l o w 4-5 C ( A l l e n 1 9 6 9 ) . A l s o , B r e t t e t a l . (1969) r e p o r t e d t h a t g r o w t h o f s o c k e y e s a l m o n ( 0 . n e r k a ) , d u r i n g t h e i r f i r s t y e a r o f l i f e , o p e a k e d b e t w e e n 5 a n d 17 C and c h i n o o k a r e p r o b a b l y c h a r a c t e r i z e d by s i m i l a r t h e r m a l l i m i t s t o g r o w t h e f f i c i e n c y . T o t a l h o u r s o f d a y l i g h t d u r i n g t h e g r o w i n g s e a s o n ( i . e . a i r t e m p e r a t u r e s >4°C) was t h e f i n a l e n v i r o n m e n t a l v a r i a b l e u s e d a s an i n d i c a t o r o f g r o w t h o p p o r t u n i t y . D i s t a n c e t o t h e s e a m e a s u r e m e n t s were d e t e r m i n e d f r o m t o p o g r a p h i c maps u s i n g a D e r b y m a p - u n i t c o u n t e r . The d a t a on v a r i a t i o n among p o p u l a t i o n s i n j u v e n i l e l i f e h i s t o r y a n d e n v i r o n m e n t a l f a c t o r s were s u m m a r i z e d by p r i n c i p a l component a n a l y s i s (PCA) o f t h e c o r r e l a t i o n m a t r i x u s i n g MIDAS ( F o x a n d G u i r e 1 9 7 6 ) . D i s t a n c e s t o t h e s e a were log,© t r a n s f o r m e d b e f o r e PCA t o r e d u c e s k e w n e s s o f t h e d a t a . P o p u l a t i o n s o v e r t h e g e o g r a p h i c r a n g e were t h e n g r o u p e d i n t o two c l a s s e s : ( i ) p r e d o m i n a n t l y (>75%) s t r e a m - t y p e o r ( i i ) p r e d o m i n a n t l y o c e a n - t y p e . M a n n - W h i t n e y U - t e s t s were u s e d t o t e s t f o r e q u a l i t y o f t h e a v e r a g e p r i n c i p a l c omponent s c o r e s f o r e a c h g r o u p u s i n g SYSTAT ( W i l k i n s o n 1 9 8 8 ) . Spearman r a n k c o r r e l a t i o n c o e f f i c e n t s were c a l c u l a t e d b e t w e e n p e r c e n t a g e s t r e a m - t y p e l i f e h i s t o r y a n d t h e p r i n c i p a l c omponent s c o r e s u s i n g SYSTAT. 156 R e s u l t s I n f o r m a t i o n on j u v e n i l e l i f e h i s t o r y v a r i a t i o n a n d e n v i r o n m e n t a l v a r i a t i o n was c o l l e c t e d f r o m a t o t a l o f 160 p o p u l a t i o n s r a n g i n g f r o m C a l i f o r n i a t o A l a s k a , K a m c h a t k a , a n d New Z e a l a n d . P r i n c i p a l c o m p o n e n t s a n a l y s i s o f t h e e n v i r o n m e n t a l v a r i a b l e s a s s o c i a t e d w i t h t h e g e o g r a p h i c l o c a t i o n s o f t h e s e s p a w n i n g a n d r e a r i n g s t r e a m s s u m m a r i z e d 96% o f t h e t o t a l v a r i a n c e i n 2 component a x e s ( T a b l e 2 2 ) . The f i r s t a x i s ( 7 9 % t o t a l v a r i a n c e ) was i n t e r p r e t e d a s c o n t r a s t i n g s t r e a m s i n t e r m s o f d i s t a n c e f r o m t h e s e a a n d d a y l i g h t h o u r s a t f r y e m e r g e n c e ( n e g a t i v e c o e f f i c i e n t s ) w i t h s t r e a m t e m p e r a t u r e and d a y l i g h t h o u r s o v e r t h e g r o w i n g s e a s o n ( p o s i t i v e c o e f f i c i e n t s ) . The s e c o n d component a x i s ( 1 7 % t o t a l v a r i a n c e ) was i n t e r p r e t e d a s a " m i g r a t i o n d i s t a n c e " c o m p o n e n t . P l o t s o f PC s c o r e s f o r s t r e a m - a n d o c e a n - t y p e p o p u l a t i o n s s u g g e s t e d c o n s i d e r a b l e s e p a r a t i o n b e t w e e n t h e l i f e h i s t o r y t y p e s a l o n g PC1, b u t l i t t l e a l o n g PC2 ( F i g . 2 4 ) . Mean PC s c o r e s b e t w e e n s t r e a m - a n d o c e a n - t y p e c h i n o o k w e r e , i n f a c t , s i g n i f i c a n t l y d i f f e r e n t a l o n g PC 1 ( M a n n - W h i t n e y U - t e s t , P < 0 . 0 0 1 ) , b u t o n l y b a r e l y a l o n g PC2 ( P = 0 . 0 5 ) . I n a d d i t i o n , p e r c e n t a g e o f t h e s t r e a m - t y p e l i f e h i s t o r y was n e g a t i v e l y c o r r e l a t e d w i t h s c o r e s a l o n g PC1 ( r s = - 0 . 8 4 , P < 0 . 0 1 ) , b u t was u n c o r r e l a t e d w i t h PC2 s c o r e s ( P > 0 . 0 5 ) . P o p u l a t i o n s t h a t t e n d t o be s t r e a m - t y p e i n j u v e n i l e l i f e 157 T a b l e 22. P r i n c i p a l c o m p o n e n t s a n a l y s i s o f e n v i r o n m e n t a l v a r i a b l e s c h a r a c t e r i s t i c o f p o p u l a t i o n s o f c h i n o o k s a l m o n . E n v i r o n m e n t a l C o e f f i c i e n t v a r i a b l e PC 1 PC2 A i r t e m p e r a t u r e 0. 531 0. 222 D i s t a n c e t o s e a - 0 . 366 0. 928 D a y l i g h t h r a t >4°C - 0 . 536 - 0 . 260 T o t a l d a y l i g h t h r 0. 545 0. 151 C u m u l a t i v e v a r i a n c e a c c o u n t e d f o r (%) 79.2 95.9 158 F i g u r e 24. P l o t o f p r i n c i p a l component s c o r e s o f s t r e a m - a n d o c e a n - t y p e p o p u l a t i o n s a l o n g component a x e s 1 a n d 2. D i s t a n c e t o s e a , mean a n n u a l a i r t e m p e r a t u r e , h o u r s o f d a y l i g h t a t f r y e m e r g e n c e , a n d t o t a l a n n u a l d a y l i g h t h o u r s have been a b b r e v i a t e d a s s e a d i s t . , temp., e m e r g e l . , and t o t a l l i g h t r e s p e c t i v e l y . a zz CO m > D co m m 33 o as" 2 o 1 o —I 3 T3 o H > S E A DIST. PC 2 (14% total variance) i K> _ 1 _ _ L _ I o Ln _ i _ o _ 1 _ o Ln _ 1 _ _ L _ • I • • • • rjUJ CP • CS • • • • • • • • O M 6ST 160 h i s t o r y tend a l s o to be l o c a t e d i n areas with a r e l a t i v e l y short growing season ( c o l d c l i m a t e s with low t o t a l d a y l i g h t hours) and to be d i s t a n t from the sea. By c o n t r a s t , ocean-type chinook p o p u l a t i o n s tend to be found i n warmer areas with long growing seasons and c l o s e r to the sea ( F i g . 24). In c e r t a i n areas, however, (Northern B. C , Al a s k a , Yukon R i v e r ) v a r i a t i o n among p o p u l a t i o n s i n d i s t a n c e to the sea i s not r e f l e c t e d i n v a r i a b i l i t y i n j u v e n i l e l i f e h i s t o r y p a t t e r n (PC2). D i s c u s s i o n Chinook salmon e x h i b i t c o n s i d e r a b l e v a r i a b i l i t y i n j u v e n i l e l i f e h i s t o r y over a wide geographic range, but there i s a l s o much v a r i a b i l i t y among nearby p o p u l a t i o n s and even between p o p u l a t i o n s w i t h i n s i n g l e t r i b u t a r i e s . Broadly speaking there are two dichotomies where v a r i a t i o n i n j u v e n i l e l i f e h i s t o r i e s appears to change a b r u p t l y (see a l s o Healey 1983). F i r s t , both o ocean- and stream-type salmon are present south of about 56 N l a t i t u d e , but only stream-type chinooks are found north of t h i s p o i n t . Second, south of 56 N a " c o a s t a l - i n t e r i o r " dichotomy i s apparent; stream-type chinook predominate i n i n t e r i o r areas (e.g. upstream of H e l l ' s Gate on the F r a s e r R i v e r and upstream of the Columbia-Snake c o n f l u e n c e on the Columbia R i v e r ) , but ocean-type chinooks predominate i n c o a s t a l streams. Perhaps more complete sampling would r e v e a l a more continuous t r a n s i t i o n from ocean- to stream-type p o p u l a t i o n s with l a t i t u d e and with i n c r e a s i n g d i s t a n c e from the sea. Many of the streams i n the 161 t r a n s i t i o n a l a r e a s a r e r e m o t e a n d h a v e o n l y r e c e n t l y b een t h e s u b j e c t o f i n v e s t i g a t i o n ( S h e p h e r d e t a l . 1 9 8 6 b ) . S a m p l i n g a l o n g c o a s t a l - i n t e r i o r t r a n s e c t s i s p e r h a p s more c o m p l e t e , b u t t h e r e a r e s t i l l c o m p a r a t i v e l y few " i n t e r m e d i a t e - t y p e " p o p u l a t i o n s . What f a c t o r s may e x p l a i n t h e o r i g i n a n d m a i n t e n a n c e o f t h e d i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r i e s i n t h e N o r t h P a c i f i c ? P o s s i b l e f a c t o r s i n c l u d e : ( i ) h i s t o r i c a l p a t t e r n s o f p o s t g l a c i a l d i s p e r s a l , ( i i ) e n v i r o n m e n t a l v a r i a b i l i t y among p o p u l a t i o n s i n " g r o w t h o p p o r t u n i t y " , a n d ( i i i ) s e l e c t i v e f a c t o r s d r i v i n g d i v e r g e n c e i n j u v e n i l e f r e s h w a t e r l i f e h i s t o r i e s . Of t h e l a t t e r f a c t o r , c h a n g e s i n f i s h i n g m o r t a l i t y may i n f l u e n c e s e l e c t i o n o f l i f e h i s t o r y t r a i t s i n s a l m o n i d s s i n c e f i s h i n g i s s i z e - s e l e c t i v e a nd s i z e i s c o r r e l a t e d w i t h many l i f e h i s t o r y t r a i t s ( R i c k e r 1981; H e a l e y 1983, 1 9 8 6 ) . T h e r e f o r e , i n some c a s e s f i s h i n g m o r t a l i t y may have i n f l u e n c e d t h e r e l a t i v e p r o p o r t i o n s o f s t r e a m - a n d o c e a n - t y p e l i f e h i s t o r i e s , b e t w e e n y e a r s o r p o p u l a t i o n s , s i n c e t h e d e v e l o p m e n t o f c o m m e r c i a l f i s h e r i e s f o r c h i n o o k . S i n c e , h o w e v e r , t h e f o c u s o f t h i s s t u d y was c o n c e r n e d w i t h b r o a d g e o g r a p h i c p a t t e r n s , c h a n g e s i n f i s h i n g m o r t a l i t y a r e n o t c o n s i d e r e d a s a s e r i o u s s o u r c e o f e r r o r o r m e c h a n i s m o f d i v e r g e n c e . F i s h s p e c i e s d i s t r i b u t i o n s a n d p a t t e r n s o f i n t r a s p e c i f i c v a r i a b i l i t y a l o n g t h e n o r t h P a c i f i c c o a s t h a v e been d o m i n a t e d by g l a c i a t i o n a n d a c c e s s r o u t e s f r o m v a r i o u s r e f u g i a ( L i n d s e y a n d 162 M c P h a i l 1986; M c P h a i l and L i n d s e y 1986). Chinook salmon p r o b a b l y s u r v i v e d the l a s t ( W i s c o n s i n a n ) g l a c i a t i o n i n two major r e f u g i a : ( i ) " B e r i n g i a " , d e f i n e d as the lower Yukon R i v e r and exposed p o r t i o n s of the B e r i n g Sea and S i b e r i a , and " C a s c a d i a " , d e f i n e d as a r e a s s o u t h of g l a c i a t i o n west of the C o n t i n e n t a l D i v i d e ( L i n d s e y and M c P h a i l 1986, M c P h a i l and L i n d s e y 1986). D u r i n g d e g l a c i a t i o n ( b e g i n n i n g about 13,500 y e a r s a g o ) , c h i n o o k d i s p e r s e d from t h e s e n o r t h e r n and s o u t h e r n r e f u g i a a l o n g the P a c i f i c c o a s t ( L i n d s e y and M c P h a i l 1986). South of the Taku o R i v e r (about 58 N) the m a j o r i t y of e x t a n t p o p u l a t i o n s were p r o b a b l y c o l o n i z e d from C a s c a d i a whereas B e r i n g i a p r o v i d e d s o u r c e p o p u l a t i o n s f o r r i v e r s n o r t h of the Taku. R i v e r s such as the Taku, Copper, and A l s e k i n s o u t h e a s t e r n A l a s k a were p r o b a b l y c o l o n i z e d by c h i n o o k t h a t p e r s i s t e d b o t h i n C a s c a d i a and B e r i n g i a ( L i n d s e y and M c P h a i l 1986); i n f a c t , s o u t h e a s t e r n A l a s k a n c h i n o o k a r e i n t e r m e d i a t e e l e c t r o p h o r e t i c a l l y between western Alaskan/Yukon R i v e r p o p u l a t i o n s and c h i n o o k i n C a s c a d i a ( G h a r r e t e t a l . 1987). T h e r e f o r e , i f chinook t h a t s u r v i v e d g l a c i a t i o n i n B e r i n g i a were p r i m a r i l y stream-type w h i l e b o t h stream- and ocean-type c h i n o o k s p e r s i s t e d i n C a s c a d i a , the l a t i t u d i n a l d i s t r i b u t i o n of l i f e h i s t o r y t y p e s i n the N o r t h P a c i f i c may, i n l a r g e p a r t , r e f l e c t p a t t e r n s of p o s t g l a c i a l d i s p e r s a l . The r a t h e r a b r u p t d i s c o n t i n u i t y i n l i f e h i s t o r y o d i s t r i b u t i o n a t about 54-56 N i s s u g g e s t i v e of a p a t t e r n r e s u l t i n g from s u r v i v a l i n , and d i p e r s a l from, i s o l a t e d r e f u g i a and i s s i m i l a r t o d i s t r i b u t i o n a l p e c u l i a r i t i e s i n some o t h e r 163 s p e c i e s ( W i t h l e r 1985; L i n d s e y a n d M c P h a i l 1 9 8 6 ) . R i v e r s s u c h a s t h e A l s e k , T a k u , a n d C o p p e r i n s o u t h e a s t e r n A l a s k a , a n d t h e S t i k i n e t h r o u g h t o t h e S k e e n a R i v e r i n n o r t h e r n B.C. were p r o b a b l y c o l o n i z e d , i n p a r t , f r o m C a s c a d i a n c h i n o o k ( i . e . b o t h s t r e a m - a n d o c e a n - t y p e ) y e t t h e y now h a v e o n l y s t r e a m - t y p e c h i n o o k . T h i s s u g g e s t s , t h e r e f o r e , t h a t some f a c t o r s o p e r a t i n g a f t e r p o s t g l a c i a l d i s p e r s a l p r o b a b l y a l s o e x p l a i n some o f t h e v a r i a t i o n i n j u v e n i l e l i f e h i s t o r y . I n f i s h e s , g r o w t h r a t e a n d / o r d i f f e r e n t i a t i o n r a t e a r e i m p o r t a n t d e t e r m i n a n t s o f t h e t i m i n g o f d e v e l o p m e n t a l t r a n s i t i o n s s u c h a s l a r v a l m e t a m o r p h o s i s , m a t u r a t i o n , a n d s m o l t i f i c a t i o n ( T h o r p e a n d Morgan 1978; P o l i c a n s k y 1983; T h o r p e 1986; C l a r k e 1987; Chambers and L e g g e t t 1 9 8 8 ) . E n v i r o n m e n t a l f a c t o r s t h a t i n f l u e n c e g r o w t h r a t e , i n p a r t i c u l a r w a t e r t e m p e r a t u r e , h a v e l o n g been c o n s i d e r e d a s d i r e c t c a u s e s o f v a r i a b i l i t y i n d u r a t i o n o f f r e s h w a t e r r e s i d e n c e b e f o r e s m o l t i f i c a t i o n ( R i c h 1925; W h i t e a n d Huntsman 1938; R a n d a l l e t a l . 1 9 8 7 ) . The s t u d i e s by C l a r k e e t a l . ( 1 9 8 8 ) , C l a r k e ( 1 9 8 7 ) , C l a r k e a n d W i t h l e r ( 1 9 8 7 ) , a n d T h o r p e e t a l . ( 1 9 8 9 ) have shown t h a t i n c r e a s e d g r o w t h r a t e i s a c c o m p a n i e d by e a r l i e r a t t a i n m e n t o f s m o l t i f i c a t i o n w i t h i n p o p u l a t i o n s . I n t h e s e s t u d i e s , t e m p e r a t u r e a n d p h o t o p e r i o d were e n v i r o n m e n t a l f a c t o r s m a n i p u l a t e d t o a c c e l e r a t e g r o w t h r a t e a n d s m o l t i f i c a t i o n t i m i n g i n y o u n g c h i n o o k a n d A t l a n t i c s a l m o n . O v e r t h e g e o g r a p h i c r a n g e o f c h i n o o k , a v e r a g e t e m p e r a t u r e s d e c r e a s e b o t h w i t h i n c r e a s i n g l a t i t u d e a n d d i s t a n c e f r o m t h e s e a . A l o n g t h e c o a s t a n d 164 p a r t i c u l a r l y a t l o w e r l a t i t u d e s , t h e number o f d a y s a t w h i c h a v e r a g e t e m p e r t u r e s e x c e e d 4 C i s g r e a t e r t h a n a t i n l a n d o r h i g h l a t i t u d e a r e a s . I n sum, g r o w i n g s e a s o n l e n g t h , a s a m e a s u r e o f " g r o w t h o p p o r t u n i t y " , i s g r e a t e r i n l o w l a t i t u d e c o a s t a l a r e a s where o c e a n - t y p e c h i n o o k p r e d o m i n a t e . C l a r k e ( 1 9 8 7) and C l a r k e a n d W i t h l e r ( 1 9 8 7 ) showed t h a t low d a y l i g h t h o u r s a t f i r s t f e e d i n g i n c r e a s e d g r o w t h a n d s m o l t i n g r a t e s i n y o u n g s t r e a m - t y p e c h i n o o k . I n l a n d a n d h i g h e r l a t i t u d e p o p u l a t i o n s o f c h i n o o k g e n e r a l l y emerge and b e g i n f e e d i n g l a t e r , u n d e r l o n g e r d a y l i g h t h o u r s , t h a n c o a s t a l o r l o w e r l a t i t u d e p o p u l a t i o n s due t o t h e c o m b i n e d e f f e c t s o f i n c r e a s i n g l a t i t u d e a n d l o w e r i n c u b a t i o n t e m p e r a t u r e s ( W a l k e r 1976; Raymond 1981; S h e p h e r d e t a l . 1 9 8 6 b ) . A s s o c i a t i o n b e t w e e n t h e d i s t r i b u t i o n o f c h i n o o k l i f e h i s t o r i e s a n d e n v i r o n m e n t a l v a r i a b i l i t y , c o u p l e d , w i t h t h e r e s u l t s f r o m s t u d i e s a d d r e s s i n g t h e l i n k s among w a t e r t e m p e r a t u r e , p h o t o p e r i o d , g r o w t h , a n d s m o l t i n g r a t e ( C l a r k e 1987; C l a r k e a n d W i t h l e r 1987; T h o r p e e t a l . 1 9 8 9 ) , s u g g e s t t h a t v a r i a t i o n i n e n v i r o n m e n t a l f a c t o r s t h a t i n f l u e n c e " g r o w t h o p p o r t u n i t y " i s c a u s a l l y r e l a t e d t o t h e d i s t r i b u t i o n o f j u v e n i l e l i f e h i s t o r i e s . The i m p o r t a n c e o f " g r o w t h o p p o r t u n i t y " i s a l s o s u g g e s t e d i n t h e s t u d y by H o l t b y ( 1 9 8 8) who d o c u m e n t e d an i n c r e a s e i n t h e p r o p o r t i o n o f c o h o s a l m o n s m o l t i n g a t 1 y e a r o f a g e , r a t h e r t h a n a t 2 y e a r s , o v e r an 8 y e a r p e r i o d i n a s m a l l c o a s t a l B.C. s t r e a m . The d e c l i n e i n t h e a v e r a g e d u r a t i o n o f f r e s h w a t e r 1 65 r e s i d e n c e by c o h o was a s s o c i a t e d w i t h i n c r e a s e d s t r e a m t e m p e r a t u r e s a nd i n c r e a s e d g r o w t h r a t e s o v e r t h e same t i m e p e r i o d ( H o l t b y 1 9 8 8 ) . S i m i l a r i n v e r s e r e l a t i o n s h i p s b e t w e e n " g r o w t h o p p o r t u n i t y " a n d s m o l t i n g age a r e o b s e r v e d i n o t h e r s a l m o n i d s i n b o t h t h e n o r t h P a c i f i c a n d A t l a n t i c ( R a n d a l l e t a l . 1987; T h o r p e e t a l . 1989; M e t c a l f e a nd T h o r p e 1989) a n d f o r l a t i t u d i n a l c l i n e s i n m e t a m o r p h o s i s t i m i n g i n u r o d e l e s a n d a n u r a n s ( S e x t o n a n d B i z e r 1978; S m i t h - G i l l a n d B e r v e n 1 9 7 9 ) . A n u r a n m e t a m o r p h o s i s a nd s a l m o n i d s m o l t i f i c a t i o n a r e s i m i l a r d e v e l o p m e n t a l t r a n s i t i o n s b e c a u s e b o t h a r e d e p e n d e n t on g r o w t h r a t e , b o t h a r e i n f l u e n c e d by t h y r o x i n e , a n d b o t h e n compass w i d e v a r i a t i o n i n t h e s i z e a n d t i m i n g o f m e t a m o r p h i c c l i m a x ( S m i t h - G i l l a n d B e r v e n 1979; T h o r p e 1 9 8 7 ) . S m i t h - G i l l a n d B e r v e n (1979) i l l u s t r a t e d how t h e d u r a t i o n o f a n u r a n l a r v a l p e r i o d s was d e t e r m i n e d l a r g e l y by e n v i r o n m e n t a l l y i n d u c e d x v a r i a t i o n i n d i f f e r e n t i a t i o n r a t e ( r >90%) w h e r e a s v a r i a t i o n i n g r o w t h r a t e was a much w e a k e r d e t e r m i n a n t o f t i m i n g o f m e t a m o r p h o s i s ( r = 5 1 % ) . D i f f e r e n t i a t i o n r a t e i s i n f l u e n c e d more s t r o n g l y t h a n g r o w t h r a t e by t e m p e r a t u r e i n a n u r a n s ; a t l o w t e m p e r a t u r e s d i f f e r e n t i a t i o n r a t e i s more s t r o n g l y r e t a r d e d t h a n g r o w t h r a t e s u c h t h a t m e t a m o r p h o s i s o c c u r s a t l a r g e r s i z e s t h a n a t h i g h e r t e m p e r a t u r e s ( S m i t h - G i l l a n d B e r v e n 1 9 7 9 ) . T h e r e f o r e , warmer c l i m a t e s a c c e l e r a t e d i f f e r e n t i a t i o n r a t e f a s t e r t h a n g r o w t h r a t e , a n d a t t a i n m e n t o f m e t a m o r p h i c c l i m a x a t s m a l l e r s i z e s ( a n d y o u n g e r a g e s ) i s i n c r e a s i n g l y p r o b a b l e ( S e x t o n a nd B i z e r 1978; S m i t h - G i l l a n d B e r v e n 1 9 7 9 ) . 166 A p a r a l l e l o b s e r v a t i o n i s t h e p r e d o m i n a n c e o f g e n e r a l l y s m a l l e r , o c e a n - t y p e c h i n o o k s m o l t s i n warmer, low l a t i t u d e , c o a s t a l c l i m a t e s . I f s m o l t i f i c a t i o n i s a l s o d i f f e r e n t i a t i o n r a t e d e p e n d e n t , t h e n c o l d e r c l i m a t e s ( h i g h e r l a t i t u d e s , i n t e r i o r a r e a s ) m i g h t r e q u i r e l o n g e r p e r i o d s o f f r e s h w a t e r r e s i d e n c e b e f o r e t h e d e v e l o p m e n t a l t r a n s i t i o n o f s m o l t i f i c a t i o n c a n be c o m p l e t e d . C o n s i d e r a t i o n o f a n u r a n m e t a m o r p h o s i s a n d d i f f e r e n t i a t i o n r a t e m i g h t e x p l a i n t h e o f t e n p o o r c o r r e l a t i o n s o b s e r v e d b e t w e e n g r o w t h r a t e a n d s m o l t i f i c a t i o n r a t e i n some s a l m o n i d p o p u l a t i o n s ( R a n d a l l e t a l . 1 9 8 7 ) , i . e . p e r h a p s d i f f e r e n t i a t i o n r a t e w o u l d be a b e t t e r p r e d i c t o r o f s m o l t i f i c a t i o n r a t e . As n o t e d by R a n d a l l e t a l . ( 1 9 8 7 ) , t h e r e a r e a few p r o b l e m s w i t h c o n c l u d i n g t h a t v a r i a t i o n i n t h e d u r a t i o n o f f r e s h w a t e r r e s i d e n c e i s l a r g e l y e n v i r o n m e n t a l l y d e t e r m i n e d . F i r s t , t h e r e a r e numerous c a s e s o f b o t h s t r e a m - a n d o c e a n - t y p e c h i n o o k i n p o p u l a t i o n s g e o g r a p h i c a l l y c l o s e t o one a n o t h e r , s o m e t i m e s o c c u p y i n g t h e same r i v e r ( e . g . F u l t o n 1968; C a r l a n d H e a l e y 1 9 8 4 ) . A t l e a s t some o f t h e s e p o p u l a t i o n s a p p e a r t o e x p e r i e n c e s i m i l a r e n v i r o n m e n t a l c o n d i t i o n s y e t t h e y e x h i b i t d i f f e r e n t j u v e n i l e l i f e h i s t o r i e s . S e c o n d , g r o w t h r a t e a n d age a t s m o l t i n g a r e n o t a l w a y s n e g a t i v e l y c o r r e l a t e d e s p e c i a l l y i n c o m p a r i s o n s among p o p u l a t i o n s ( R i c k e r 1972; R a n d a l l e t a l . 1 9 8 7 ) . 167 T h i r d , t h e r e i s m o u n t i n g e v i d e n c e t h a t s t r e a m - a n d o c e a n -t y p e c h i n o o k a r e g e n e t i c a l l y d i s t i n c t f r o m one a n o t h e r . F o r i n s t a n c e , H e a l e y ( 1 9 8 3 ) , C a r l a n d H e a l e y ( 1 9 8 4 ) , a n d T a y l o r ( 1 9 8 9 ) s u m m a r i z e d a n d p r e s e n t e d d a t a t h a t s u g g e s t e d t h a t s t r e a m -a n d o c e a n - t y p e c h i n o o k a r e d i v e r g e n t i n s e v e r a l t r a i t s , e . g . o c e a n i c m i g r a t i o n b e h a v i o u r , m o r p h o l o g y , a l l o z y m e f r e q u e n c i e s , a n d r a t e o f m a l e p r e c o c i a l m a t u r a t i o n . Many o f t h e s e t r a i t s , a n d o t h e r s ( C h a p t e r 1 ) , a p p e a r t o be f u n c t i o n a l l y i m p o r t a n t f o r d i f f e r e n t d u r a t i o n s o f s t r e a m r e s i d e n c e b e f o r e s e a w a r d m i g r a t i o n . G e n e t i c v a r i a t i o n i n t r a i t s c o r r e l a t e d w i t h f r e s h w a t e r l i f e h i s t o r y i s t o be e x p e c t e d i f v a r i a b i l i t y i n d u r a t i o n o f f r e s h w a t e r r e s i d e n c e i s i t s e l f i n h e r i t e d . R i c h a n d Holmes ( 1 9 2 8 ) f o u n d p o s i t i v e c o r r e l a t i o n s b e t w e e n p a r e n t a nd p r o g e n y a g e , a n d s i z e , a t s e a w a r d m i g r a t i o n i n s e v e r a l C o l u m b i a R i v e r c h i n o o k p o p u l a t i o n s . T h e s e c o r r e l a t i o n s were o b s e r v e d e v e n when j u v e n i l e s were r e l e a s e d i n t o s t r e a m s where t h e n a t i v e s a l m o n m i g r a t e d s e a w a r d a t a d i f f e r e n t t i m e t h a n t h e t r a n s p l a n t s . I n a d d i t i o n , s t r e a m - t y p e c h i n o o k a r e u s u a l l y t h e p r o g e n y o f " s p r i n g - r u n " a d u l t s a l m o n w h e r e a s o c e a n - t y p e c h i n o o k a r e t y p i c a l l y p r o d u c e d by " f a l l - r u n " a d u l t s ( R i c h a n d Holmes 1928; R i c k e r 1972; C a r l a n d H e a l e y 1 9 8 4 ) . S i n c e a d u l t c h i n o o k m i g r a t i o n t i m i n g i s i n h e r i t e d ( R i c h a n d Holmes 1928; R i c k e r 1972) t h e a s s o c i a t e d j u v e n i l e m i g r a t i o n b e h a v i o u r s m i g h t a l s o be g e n e t i c a l l y c o n t r o l l e d . F i n a l l y , s t u d i e s on s p e c i e s o t h e r t h a n c h i n o o k s a l m o n have a l s o i m p l i c a t e d g e n o t y p e a s a d e t e r m i n a n t o f f r e s h w a t e r l i f e h i s t o r y ( R i c k e r 1972; 1978; R e f s t i e e t a l . 1977; T h o r p e a n d M o r g a n 1978; T h o r p e e t a l . 1 9 8 3 ) . 168 I t i s , t h e r e f o r e , s t r o n g l y s u g g e s t e d t h a t v a r i a b i l i t y i n j u v e n i l e l i f e h i s t o r y p a t t e r n i s , a t l e a s t i n p a r t , i n h e r i t e d . What f a c t o r s , t h e n , m i g h t d r i v e a n d m a i n t a i n d i v e r g e n c e i n d u r a t i o n o f f r e s h w a t e r r e s i d e n c e among p o p u l a t i o n s ? M i g r a t i o n d i s t a n c e , a s a m e a s u r e o f m i g r a t i o n d i f f i c u l t y , h a s r e p e a t e d l y been i m p l i c a t e d a s a m a j o r s e l e c t i v e f a c t o r d r i v i n g d i v e r g e n c e i n m o r p h o l o g i c a l , b e h a v i o u r a l , p h y s i o l o g i c a l , and l i f e h i s t o r y t r a i t s among anadromous f i s h p o p u l a t i o n s ( R o b e r t s o n 1957; R i c k e r 1972; S c h a f f e r a n d E l s o n 1975; G l e b e a n d L e g g e t t 1976; Y e v s i n 1977; T a y l o r a n d M c P h a i l I 9 8 5 a , b ; T a y l o r 1 9 8 9 ) . I n c r e a s e d m i g r a t i o n d i s t a n c e i s a s s o c i a t e d w i t h g r e a t e r e n e r g y r e s e r v e s , e n e r g y e x p e n d i t u r e , a n d l a r g e r body s i z e i n a d u l t s a l m o n i d s ( R i c h a n d Holmes 1928; G i l h o u s e n 1980; S c h a f f e r a n d E l s o n 1975; T h o r p e a n d M i t c h e l l 1 9 8 1 ) , a n d i n c r e a s e d p r o l o n g e d swimming c a p a b i l i t i e s i n j u v e n i l e s ( T s u y u k i a n d W i l l i s c r o f t 1977; T a y l o r a n d M c P h a i l 1 9 8 5 b ) . T h e s e s t u d i e s t a k e n t o g e t h e r s u g g e s t t h a t i n c r e a s e d m i g r a t i o n d i s t a n c e i m p o s e s g r e a t e r e n e r g e t i c demands on m i g r a n t s a n d , g i v e n i n c r e a s e d p r o l o n g e d swimming c a p a b i l i t y w i t h i n c r e a s i n g f i s h s i z e ( B r e t t a n d G l a s s 1973; Webb 1 9 7 8 ) , l a r g e r i n d i v i d u a l s a r e p r o b a b l y b e t t e r a b l e t o c o m p l e t e l o n g e r , a r d u o u s m i g r a t i o n s . P r e d a t i o n on f r e s h w a t e r m i g r a n t s c a n be s u b s t a n t i a l ( H u n t e r 1959; Wood 1985) a n d l o n g e r s m o l t m i g r a t i o n s may i m p o s e g r e a t e r f r e s h w a t e r p r e d a t i o n r i s k ( e . g . L a r s s o n 1985; R u g g e r t o n e 1 9 8 6 ) . 169 S i n c e s m a l l e r s a l m o n a r e more s u s c e p t i b l e t o p r e d a t i o n ( e . g . H a r g r e a v e s ' a n d L e B r a s s e u r 1 9 8 7 ) , l a r g e r s m o l t s m i g h t e x p e r i e n c e l o w e r m o r t a l i t y r a t e s f r o m p r e d a t i o n d u r i n g m i g r a t i o n . I n a d d i t i o n , o s m o r e g u l a t o r y a b i l i t y i n c r e a s e s w i t h f i s h s i z e ( e . g . M c C o r m i c k a n d Naiman 1984b) a n d l a r g e r s i z e a t o c e a n e n t r y p r o b a b l y e n h a n c e s p h y s i o l o g i c a l a d j u s t m e n t t o h i g h s a l i n i t i e s a f t e r e n e r g e t i c a l l y d e m a n d i n g m i g r a t i o n s . T h e s e p o t e n t i a l s i z e - r e l a t e d d e t e r m i n a n t s o f " m i g r a t i o n s u c c e s s " a l l s u g g e s t t h a t i n c r e a s i n g m i g r a t i o n d i s t a n c e m i g h t s e l e c t f o r i n c r e a s e d s i z e a t m i g r a t i o n i n a n a d r o m o u s p o p u l a t i o n s . I n t e r e s t i n g l y , C l a r k e (1987) f o u n d t h a t he c o u l d m a n i p u l a t e p h o t o p e r i o d t o i n c r e a s e t h e r a t e o f g r o w t h a nd s m o l t i n g . i n s t r e a m - t y p e c h i n o o k , b u t t h e s e s a l m o n , f r o m a p o p u l a t i o n 600 km u p s t r e a m f r o m t h e s e a , w e i g h e d 10 g a t s m o l t i f i c a t i o n . By c o n t r a s t , t h e o c e a n - t y p e c h i n o o k s t u d i e d by C l a r k e were f r o m a c o a s t a l s t r e a m a n d t h e y s m o l t e d a t 5 g. P r o l o n g e d swimming a b i l i t y a n d o s m o r e g u l a t o r y a b i l i t y may a l s o be r e d u c e d a t low w a t e r t e m p e r a t u r e s ( B r e t t 1967; B e a m i s h 1978; V i r t a n e n a n d O i k a r i 1 9 8 4 ) . T h e r e f o r e , l a r g e s i z e a t o c e a n e n t r y m i g h t be f a v o u r e d by s e l e c t i o n i n c h i n o o k p o p u l a t i o n s l o c a t e d i n c o l d c l i m a t e s . I n sum, t h e r e i s c o n s i d e r a b l e p o t e n t i a l f o r s e l e c t i o n on s i z e a t m i g r a t i o n i n c h i n o o k p o p u l a t i o n s . C o n s e q u e n t l y , e n v i r o n m e n t a l v a r i a b i l i t y among p o p u l a t i o n s p r o b a b l y r e s u l t s i n 170 s e l e c t i o n f o r o p t i m a l s m o l t s i z e s t h a t v a r y among p o p u l a t i o n s ( R i c k e r 1 9 7 2 ) . E x c e p t i n s i t u a t i o n s where p o p u l a t i o n s h a v e s i m i l a r s m o l t s i z e s , c o n t r o l o f s m o l t i f i c a t i o n t i m i n g f r o m d i f f e r e n c e s i n e n v i r o n m e n t a l " g r o w t h o p p o r t u n i t y " may n o t be t h e u l t i m a t e c a u s e o f v a r i a b i l i t y among p o p u l a t i o n s i n d u r a t i o n o f f r e s h w a t e r r e s i d e n c e . G r o w t h o p p o r t u n i t y may be a p r o x i m a t e f a c t o r , c o n t r o l l i n g t h e r a t e a t w h i c h p o p u l a t i o n - s p e c i f i c s i z e t h r e s h o l d s a r e a c h i e v e d . S e l e c t i o n f o r s i z e a t m i g r a t i o n c o u p l e d w i t h s e l e c t i o n f o r m i g r a t i o n d u r i n g s e a s o n a l m i g r a t i o n "windows" ( W a l t e r s e t a l . 1978; L a n n a n 1980; B i l t o n e t a l . 1982; G o d i n 1982; M i l l e r a n d B r a n n o n 1982; H o l t b y 1988) m i g h t p r o m o t e d i v e r g e n c e i n a l t e r n a t i v e j u v e n i l e l i f e h i s t o r i e s . I n p o p u l a t i o n s where i n d i v i d u a l s a c h i e v e s m o l t s i z e e a r l y , o w i n g t o f a v o u r a b l e g r o w t h c o n d i t i o n s a n d / o r s m a l l s i z e t h r e s h o l d s , s e l e c t i o n may f a v o u r an o c e a n - t y p e l i f e h i s t o r y g i v e n f a v o u r a b l e g r o w t h c o n d i t i o n s i n e s t u a r i e s r e l a t i v e t o f r e s h w a t e r h a b i t a t s ( R e i m e r s 1973; Bachman 1982; C o n g l e t o n e t a l . 1982; K j e l s o n e t a l . 1 9 8 2 ) . By c o n t r a s t , i n a r e a s where l a r g e r s m o l t s i z e i s a s s o c i a t e d w i t h h i g h e r s u r v i v a l , a n d / o r g r o w t h c o n d i t i o n s a r e l i m i t e d s u c h t h a t t h r e s h o l d s i z e s a r e n o t r e a c h e d by t h e s p r i n g / s u m m e r m i g r a t i o n window, n a t u r a l s e l e c t i o n may f a v o u r e x t e n d e d s t r e a m r e s i d e n c e r a t h e r t h a n s e a w a r d m i g r a t i o n a t u n f a v o u r a b l e t i m e s . I n c o n c l u s i o n , c o v a r i a t i o n b e t w e e n g e o g r a p h i c d i s t r i b u t i o n o f s t r e a m - a n d o c e a n - t y p e c h i n o o k a n d e n v i r o n m e n t a l f a c t o r s 171 i n f l u e n c i n g "growth o p p o r t u n i t y " , coupled with experimental r e s u l t s demonstrating e f f e c t s of environmental v a r i a b l e s on smolting r a t e , are c o n s i s t e n t with environmental modulation ( S m i t h - G i l l 1983) c o n t r i b u t i n g to v a r i a b i l i t y i n d u r a t i o n of freshwater r e s i d e n c e among chinook p o p u l a t i o n s . V a r i a t i o n i n j u v e n i l e freshwater l i f e h i s t o r i e s i s , however, at l e a s t p a r t i a l l y i n h e r i t e d , and a dominant r o l e f o r modulation of s m o l t i f i c a t i o n r a t e by environment i s probably c o n s t r a i n e d by s e l e c t i o n f o r both s i z e at m i g r a t i o n and f o r seasonal optima i n the timing of downstream m i g r a t i o n and ocean e n t r y . 172 CHAPTER 3: BEHAVIOURAL INTERACTION BETWEEN J U V E N I L E COHO AND CHINOOK SALMON AND CHINOOK L I F E HISTORY I n t r o d u c t i o n T h i s c h a p t e r i s c o n c e r n e d w i t h e v a l u a t i n g t h e h y p o t h e s i s t h a t b e h a v i o u r a l i n t e r a c t i o n w i t h j u v e n i l e c o h o s a l m o n ( O n c o r h y n c h u s k i s u t c h ) i n f l u e n c e s d u r a t i o n o f f r e s h w a t e r r e s i d e n c e by c h i n o o k . G i v e n t h e p r o x i m i t y o f c o a s t a l s t r e a m s t o p r o d u c t i v e e s t u a r i n e a r e a s a n d t h e a b i l i t y o f c h i n o o k t o a c c l i m a t e r a p i d l y t o s a l i n e w a t e r s ( W e i s b a r t 1 9 6 8 ) , c o a s t a l c h i n o o k m i g h t u n d e r t a k e e a r l y m i g r a t i o n s t o r e s i d e i n e s t u a r i n e a r e a s t o r e d u c e t h e c o s t s o f b e h a v i o u r a l i n t e r a c t i o n w i t h c o h o . More g e n e r a l l y , v a r i a b i l i t y i n b i o t i c ( i . e . c o m p e t i t i v e ) e n v i r o n m e n t s c o u l d e x p l a i n some o f t h e v a r i a t i o n i n d u r a t i o n o f f r e s h w a t e r r e s i d e n c e among c h i n o o k p o p u l a t i o n s . O v e r t h e i r g e o g r a p h i c r a n g e , j u v e n i l e c h i n o o k s a l m o n may c o e x i s t i n f r e s h w a t e r h a b i t a t s w i t h a t l e a s t f o u r o t h e r s p e c i e s o f O n c o r h y n c h u s , a s w e l l a s s t e e l h e a d a n d c u t t h r o a t t r o u t s ( S a l m o g a i r d n e r i a n d S. c l a r k i i ) , c h a r r ( S a l v e l i n u s malma a n d S. a l p i n u s ) , a n d v a r i o u s w h i t e f i s h ( C o r e g o n i n a e ) . C h i n o o k may a l s o o c c u r s y m p a t r i c a l l y w i t h s e v e r a l c y p r i n i f o r m f i s h e s (minnows a n d s u c k e r s ) , a t l e a s t one o f w h i c h may i n t e r a c t b e h a v i o u r a l l y w i t h c h i n o o k ( i . e . r e d s i d e s h i n e r , R i c h a r d s o n i u s  b a l t e a t u s ( H i l l m a n e t a l . 1 9 8 8 ) ) . F o r s e v e r a l r e a s o n s , h o w e v e r , i n t e r a c t i o n w i t h c o h o s a l m o n h a s t h e g r e a t e s t p o t e n t i a l t o 173 i n f l u e n c e f r e s h w a t e r r e s i d e n c e b e h a v i o u r o f c h i n o o k . Coho have a n a t u r a l d i s t r i b u t i o n t h a t i s b r o a d l y s i m i l a r t o t h a t o f c h i n o o k i n t h e n o r t h P a c i f i c . A l s o , l i k e c h i n o o k s a l m o n , c o h o a r e anadromous a n d r e s i d e p r i m a r i l y i n r i v e r s a n d s t r e a m s , b u t g e n e r a l l y f o r a l o n g e r t i m e ( a t l e a s t 1 y e a r ) . G i v e n t h e i r p r o l o n g e d p e r i o d o f f r e s h w a t e r r e s i d e n c e a n d t h e i r t e r r i t o r i a l a n d a g g r e s s i v e n a t u r e , c o h o a p p e a r be t h e most " s t r e a m - t y p e " o f e a s t e r n P a c i f i c O n c o r h y n c h u s (Hoar 1976; M i l l e r a n d B r a n n o n 1 9 8 2 ) . C o m p a r a t i v e s t u d i e s o f m o r p h o l o g y , p h y s i o l o g y , b e h a v i o u r , a n d b i o c h e m i c a l g e n e t i c s have i n d i c a t e d t h a t c o h o a n d c h i n o o k a r e p r o b a b l y more c l o s e l y r e l a t e d t o e a c h o t h e r t h a n t o t h e o t h e r s p e c i e s o f O n c o r h y n c h u s ( B r e t t 1952; H i k i t a 1962; T s u y u k i a n d R o b e r t s 1966; U t t e r e t a l . 1973; M c C o r m i c k a n d S a u n d e r s 1987; Thomas e t a l . 1 9 8 6 ) . S t u d i e s o f b e h a v i o u r a n d g e n e r a l e c o l o g y a l s o s u g g e s t many s i m i l a r i t i e s b e t w e e n c o h o a n d c h i n o o k ( R o u s e n f e l l 1958; R e i m e r s 1968; S t e i n e t a l . 1972; J o h n s o n 1981; J o h n s o n a n d R i n g l e r 1 9 8 1 ) . G i v e n t h e i r s y m p a t r i c o c c u r r e n c e i n many a r e a s a n d t h e i r s i m i l a r i t i e s i n b e h a v i o u r a n d e c o l o g y , b e h a v i o u r a l i n t e r a c t i o n s b e t w e e n c o h o a nd c h i n o o k m i g h t w e l l i n f l u e n c e a s p e c t s o f t h e i r f r e s h w a t e r l i f e . h i s t o r i e s . Coho a n d c h i n o o k a r e f o u n d t o g e t h e r i n many s t r e a m s i n s o u t h e r n B r i t i s h C o l u m b i a , W a s h i n g t o n , a n d O r e g o n . C o a s t a l s t r e a m s commonly s u p p o r t b o t h c o h o a n d o c e a n - t y p e c h i n o o k , b u t i n i n t e r i o r s t r e a m s , where s t r e a m - t y p e c h i n o o k p r e d o m i n a t e , c o h o 174 p o p u l a t i o n s a r e s m a l l e r and l e s s a b u n d a n t ( A r o a n d S h e p a r d 1967; A t k i n s o n e t a l . 1 9 6 7 ) . S t e i n e t a l . ( 1 9 72) d o c u m e n t e d b e h a v i o u r a l d o m i n a t i o n o f c h i n o o k by c o h o i n a s m a l l , c o a s t a l O r e g o n s t r e a m . T h e s e a u t h o r s c o n c l u d e d t h a t i n t e r a c t i o n w i t h c o h o i m p a c t e d n e g a t i v e l y on c h i n o o k . I n many s p e c i e s , i n c l u d i n g f i s h e s , a b e h a v i o u r a l l y d o m i n a n t s p e c i e s h a s been shown t o i n f l u e n c e t h e h a b i t a t u s e a n d d i s p e r s a l t e n d e n c i e s o f a s u b o r d i n a t e ( O r i a n s a n d W i l l s o n 1964; Brown 1971; J a e g e r 1971; W erner and H a l l 1977; G a i n e s e t a l . 1979; H i x o n 1980; F a u s c h a n d W h i t e 1981; L i n z e y 1 9 8 4 ) . E v i d e n c e f o r s u c h " a s y m m e t r i c " r e l a t i o n s h i p s ( M o r s e 1974) i s w i d e s p r e a d i n s a l m o n i d f i s h e s . I n s e v e r a l i n s t a n c e s i t h a s been s u g g e s t e d t h a t b e h a v i o u r a l d o m i n a t i o n o f one s p e c i e s by a n o t h e r was r e s p o n s i b l e f o r d i f f e r e n c e s i n r e s o u r c e u s e ( K a l l e b e r g 1958; H a r t m a n 1965; N o r t h c o t e a n d N i l s s o n 1981; C u n j a c k a n d G r e e n 1984; G l o v a 1986; H i n d a r e t a l . 1 9 8 8 ) . I f t h e h y p o t h e s i s t h a t c o h o i n f l u e n c e t h e f r e s h w a t e r r e s i d e n c e b e h a v i o u r o f c h i n o o k i s c o r r e c t , t h e n i t i s e x p e c t e d t h a t : ( i ) c o h o s h o u l d be d o m i n a n t d u r i n g b e h a v i o u r a l i n t e r a c t i o n w i t h c h i n o o k , a n d ( i i ) c o h o s h o u l d i n f l u e n c e b o t h t h e u s e o f m i c r o h a b i t a t s a n d t h e r e s i d e n c e t e n d e n c y o f c h i n o o k i n s t r e a m e n v i r o n m e n t s . T h e s e e x p e c t a t i o n s w e re e v a l u a t e d b y : ( i ) e x a m i n i n g b e h a v i o u r a l i n t e r a c t i o n a n d d o m i n a n c e r e l a t i o n s h i p s b e t w e e n c h i n o o k a n d c o h o j u v e n i l e s u n d e r c o n t r o l l e d c o n d i t i o n s a n d ( i i ) a s s e s s i n g t h e i n f l u e n c e o f c o h o on h a b i t a t u s e a n d 175 emigration tendency of chinook i n undisturbed and e x p e r i m e n t a l l y manipulated p o p u l a t i o n s . 176 1. SOCIAL INTERACTION BETWEEN J U V E N I L E CHINOOK AND COHO SALMON M e t h o d s B e h a v i o u r a l o b s e r v a t i o n s To s t u d y b e h a v i o u r a l i n t e r a c t i o n a n d r e l a t i v e d o m i n a n c e b e t w e e n t h e s p e c i e s , j u v e n i l e c h i n o o k a n d c o h o s a l m o n were o b s e r v e d t o g e t h e r i n s t r e a m t a n k s . B e h a v i o u r a l t e s t s were c o n d u c t e d i n 1985 u s i n g w i l d c h i n o o k f r y f r o m S l i m C r e e k ( s t r e a m - t y p e ) a n d H a r r i s o n R i v e r ( o c e a n - t y p e ) a n d c o h o f r y f r o m T i n Can C r e e k , a s m a l l s t r e a m d r a i n i n g i n t o t h e S t r a i t o f G e o r g i a n e a r t h e n o r t h arm o f t h e F r a s e r R i v e r e s t u a r y . D u r i n g 1986, l a b o r a t o r y - r e a r e d c h i n o o k f r o m S l i m C r e e k , E a g l e , H a r r i s o n , a n d Nanaimo ( f a l l r u n ) r i v e r s were s t u d i e d w i t h c o h o f r o m B l a c k C r e e k , a s m a l l s t r e a m d r a i n i n g i n t o t h e S t r a i t o f G e o r g i a n e a r C o u r t e n a y , B.C. on e a s t - c e n t r a l V a n c o u v e r I s l a n d . o B e h a v i o u r a l o b s e r v a t i o n s (10-11 C) were c o n d u c t e d on e a c h p o p u l a t i o n u s i n g e i g h t c h i n o o k a n d e i g h t c o h o f r y p l a c e d t o g e t h e r i n s t r e a m t a n k s . The t e s t s were i d e n t i c a l t o t h e s i n g l e s p e c i e s t e s t s d e s c r i b e d i n C h a p t e r 1 and c o n s i s t e d o f r e c o r d i n g b e h a v i o u r s t w i c e d a i l y f o r f i v e c o n s e c u t i v e d a y s . B e h a v i o u r a l o b s e r v a t i o n s were i n two c a t e g o r i e s f o r e a c h s p e c i e s t o w a r d s t h e o t h e r : (1) o v e r t b e h a v i o u r s ( a p p r o a c h , n i p , c h a r g e , a n d c h a s e ) a nd (2) d i s p l a y b e h a v i o u r s ( l a t e r a l a n d wigwag d i s p l a y s ) . I n e a c h t e s t mean s i z e s o f c o h o a n d c h i n o o k f r y were 177 w i t h i n 1 mm o f e a c h o t h e r and r a n g e d b e t w e e n 34 a n d 37 mm ( S L ) . S t a t i s t i c a l a n a l y s i s D a t a a n a l y s i s c o n s i s t e d o f summing t h e o v e r t a n d d i s p l a y b e h a v i o u r d u r a t i o n s by s p e c i e s a n d c a l c u l a t i n g an " i n t e r s p e c i f i c a g g r e s s i o n i n d e x " f o r e a c h o b s e r v a t i o n p e r i o d . T h i s i n d e x was t h e r a t i o o f a l l a g g r e s s i o n by c h i n o o k d i r e c t e d t o w a r d s c o h o t o t h a t o f c o h o d i r e c t e d t o w a r d s c h i n o o k . Any i n d e x o f v a l u e l e s s t h a n 1, t h e r e f o r e , i n d i c a t e s g r e a t e r a g g r e s s i o n d i r e c t e d t o w a r d s c h i n o o k by c o h o t h a n v i c e v e r s a a n d s u g g e s t s d o m i n a t i o n o f c h i n o o k by c o h o . A g g r e s s i o n i n d i c e s were c a l c u l a t e d f o r e a c h c h i n o o k p o p u l a t i o n and c o m p a r e d t o t h e v a l u e 1 by t . - t e s t s . R e s u l t s I n t h e s t r e a m t a n k s , c o h o f r y t e n d e d t o d o m i n a t e c h i n o o k f r y ( F i g . 2 5 ) . I n t e r s p e c i f i c a g g r e s s i o n i n d i c e s i n a l l t r i a l s w e re b e l o w 1, i n d i c a t i n g c o h o s p e n t more t i m e d i r e c t i n g a g g r e s s i o n t o w a r d s c h i n o o k t h a n v i c e v e r s a . Coho f r y t e n d e d t o i n i t i a t e most a g g r e s s i v e e n c o u n t e r s by c h a r g i n g a n d n i p p i n g c h i n o o k t h a t e n t e r e d " t e r r i t o r i e s " o f i n d i v i d u a l c o h o . By c o n t r a s t , most c h i n o o k a g g r e s s i o n a p p e a r e d t o be r e t a l i a t o r y ; t h e y r e s p o n d e d t o d i r e c t a t t a c k s by c o h o w i t h b r i e f d i s p l a y s , a p p r o a c h e s , a n d t h e n f l e d . D u r i n g b e h a v i o u r a l o b s e r v a t i o n s , a d o m i n a n t i n d i v i d u a l 178 F i g u r e 25. I n t e r s p e c i f i c a g g r e s s i o n i n d i c e s between coho and chinook salmon f r y . Values (mean+SE, n=3 f o r each p o p u l a t i o n ) s i g n i f i c a n t l y l e s s than 1 (denoted by a s t a r ) i n d i c a t e domination by coho salmon. S l i m Creek and Eagle River chinook are stream-type, Nanaimo and H a r r i s o n r i v e r salmon are ocean-type. INTERSPECIFIC AGGRESSION INDEX o i o o cn i o bo i O o o ~D O cz TO -i > TO 6LI QSDI m I to z > > r ; > £ x> s z n — o — < Z m < Pi 180 c o u l d u s u a l l y be i d e n t i f i e d a s t h a t w h i c h " p a t r o l l e d " t h e u p s t r e a m p o r t i o n o f t h e t a n k s e c t i o n (where f o o d was i n t r o d u c e d ) and i n i t i a t e d most a g g r e s s i o n . I n t r i a l s w i t h w i l d a n d l a b o r a t o r y - r e a r e d s a l m o n t h i s i n d i v i d u a l was a l w a y s a c o h o . I n a few c a s e s where a s i n g l e d o m i n a n t c o u l d n o t be i d e n t i f i e d , t h e c h o i c e was u s u a l l y b e t w e e n 1-3 c o h o f r y . A c h i n o o k was n e v e r t h e d o m i n a n t i n d i v i d u a l i n t h e s t r e a m t a n k s . C h i n o o k f r y ( a n d s u b d o m i n a n t c o h o ) were more r e s t r i c t e d i n t h e i r s t r e a m t a n k d i s t r i b u t i o n ; t h e y were u s u a l l y f o u n d a l o n g t h e t a n k m a r g i n s o r i n t h e d o w n s t r e a m t w o - t h i r d s o f e a c h t a n k . W h i l e c o h o t e n d e d t o d o m i n a t e c h i n o o k , t h e r e a p p e a r e d t o be d i f f e r e n c e s among t h e f o u r c h i n o o k p o p u l a t i o n s i n t h e d e g r e e o f " d o m i n a t i o n " by c o h o . S l i m C r e e k c h i n o o k d i d b e s t a g a i n s t c o h o w h i l e b o t h w i l d a nd l a b o r a t o r y - r e a r e d f i s h f r o m H a r r i s o n R i v e r h ad t h e l o w e s t i n t e r s p e c i f i c a g g r e s s i o n i n d i c e s ( F i g . 2 5 ) . 181 2. MICROHABITAT USE BY J U V E N I L E CHINOOK SALMON I N ALLOPATRY AND SYMPATRY WITH COHO SALMON M e t h o d s S n o r k e l l i n g s u r v e y s t o i d e n t i f y m i c r o h a b i t a t s o c c u p i e d by j u v e n i l e s a l m o n were c o n d u c t e d i n f o u r s t u d y s t r e a m s d u r i n g two summers. D u r i n g 1985, m i c r o h a b i t a t u s e by a l l o p a t r i c c h i n o o k f r o m S l i m C r e e k a n d by c h i n o o k s y m p a t r i c w i t h c o h o s a l m o n i n t h e E a g l e R i v e r was r e c o r d e d . M i c r o h a b i t a t s u r v e y s were e x p a n d e d i n 1986 t o i n c l u d e j u v e n i l e s a l m o n i n E a g l e R i v e r , S l i m C r e e k , a l l o p a t r i c c h i n o o k i n W a l k e r C r e e k ( s e e F i g . 1, p. 1 1 ) , a n d c o h o an d c h i n o o k i n t h e Salmon R i v e r . C h i n o o k i n a l l s t r e a m s h a v e a s t r e a m - t y p e l i f e h i s t o r y . M i c r o h a b i t a t s were r e c o r d e d d u r i n g A u g u s t when s t r e a m f l o w s , a n d h e n c e h a b i t a t a r e a , were a p p r o a c h i n g a n n u a l m i n i m a i n t h e s t u d y s t r e a m s , a n d t h u s b o u n d a r i e s b e t w e e n h a b i t a t t y p e s were d i s t i n c t . T r a n s e c t s i t e s were s e l e c t e d i n s e c t i o n s o f e a c h r i v e r s u c h t h a t a s i m i l a r r a n g e o f h a b i t a t s was s a m p l e d i n e a c h . T r a n s e c t s w ere 10 m i n l e n g t h a n d l o c a t e d i n " s i d e c h a n n e l " , " p o o l " , " r u n " , and " r i f f l e " h a b i t a t s 24 h p r i o r t o o b s e r v a t i o n . The h a b i t a t t y p e s were d i s t i n g u i s h e d by w a t e r v e l o c i t y : s i d e c h a n n e l s ( 0 - 5 c m / s ) , p o o l s ( 5 - 1 5 c m / s ) , r u n s ( 1 5 - 2 5 c m / s ) , a n d r i f f l e s (> 30 c m / s ) , b u t i n t h e same s e q u e n c e h a b i t a t s a l s o v a r i e d i n d e c r e a s i n g a v e r a g e d e p t h , amount o f c o v e r , a n d i n c r e a s i n g a v e r a g e s u b s t r a t e s i z e s . S t a r t i n g a b o u t 10 m d o w n s t r e a m o f a 182 t r a n s e c t , I swam u p s t r e a m and m a r k e d , w i t h f l a g g e d s p i k e s , t h e " h o l d i n g " o r " f o c a l " p o s i t i o n (Wickham 1967, c i t e d i n E v e r e s t a n d Chapman 1972) o f e a c h f i s h e n c o u n t e r e d w i t h i n 1.5 m o f e i t h e r s i d e o f t h e t r a n s e c t . P h y s i c a l c h a r a c t e r i s t i c s ( T a b l e 23) o f e a c h " s p i k e d " m i c r o h a b i t a t were r e c o r d e d a f t e r swimming t r a n s e c t s . The v a r i a b l e s m e a s u r e d were t h o s e t h a t h a v e been f o u n d t o be i m p o r t a n t d e t e r m i n a n t s o f m i c r o h a b i t a t u s e by s t r e a m f i s h e s ( E v e r e s t a n d Chapman 1972; M o y l e a n d B a l t z 1985; D e G r a a f a n d B a i n 1986; G rossman and Freeman 1 9 8 7 ) . A l l w a t e r v e l o c i t i e s were d e t e r m i n e d w i t h B e t z e l f l o w m e t e r s ( E v e r e s t 1 9 6 7 ) . S u b s t r a t e was q u a n t i f i e d by v i s u a l l y e s t i m a t i n g t h e r e l a t i v e p r o p o r t i o n s of two d o m i n a n t c a t e g o r i e s ( T a b l e 23) w i t h i n a 15 cm r a d i u s o f e a c h f o c a l p o s i t i o n . A summary s u b s t r a t e s c o r e was e x p r e s s e d a s t h e c o d e f o r t h e most d o m i n a n t c a t e g o r y f o l l o w e d by a d e c i m a l a n d t h e c o d e o f t h e n e x t most d o m i n a n t s u b s t r a t e c a t e g o r y . F o r e x a m p l e , a c o d e o f 5.2 i n d i c a t e s a m i c r o h a b i t a t c h a r a c t e r i z e d p r i m a r i l y by g r a v e l a n d s e c o n d a r i l y by mud. To d e t e r m i n e i f f i s h were u s i n g m i c r o h a b i t a t s w h i c h d i f f e r e d f r o m t h o s e g e n e r a l l y a v a i l a b l e , t e n p o s i t i o n s a l o n g t h e l e n g t h o f e a c h t r a n s e c t were c h o s e n f r o m a random number t a b l e ( d i s t a n c e a l o n g t r a n s e c t , l a t e r a l d i r e c t i o n a n d d i s t a n c e f r o m t r a n s e c t , d i s t a n c e a b o v e s u b s t r a t e ) . The c h a r a c t e r i s t i c s o f t h e s e "random" p o s i t i o n s were r e c o r d e d t o c ompare w i t h t h o s e o c c u p i e d by f i s h . M i c r o h a b i t a t s were r e c o r d e d f o r t h o s e f i s h o f a p p r o x i m a t e l y 183 T a b l e 23. P h y s i c a l m i c r o h a b i t a t s . m e a s u r e m e n t s r e c o r d e d a t f i s h V a r i a b l e D e f i n i t i o n F o c a l v e l o c i t y (V) Maximum v e l o c i t y (Vmax) W a t e r d e p t h (Z) D i s t a n c e t o b o t t o m (Zb) D i s t a n c e t o c o v e r ( Z c o v ) D i s t a n c e t o s h o r e ( Z s h ) S u b s t a t e : 1 2 3 4 5 6 7 8 9 W a t e r v e l o c i t y Maximum w a t e r v e l o c i t y w i t h i n 0.3 m o f f o c a l p o i n t W a t e r d e p t h D i s t a n c e o f f i s h t o s t r e a m b o t t o m S t r a i g h t l i n e d i s t a n c e b e t w e e n f o c a l p o i n t a n d n e a r e s t c o v e r u n d e r w h i c h f i s h i s i n v i s i b l e f r o m a b o v e S t r a i g h t l i n e s h o r e l i n e D e t r i t u s Mud S i l t S and G r a v e l G r a v e l R u b b l e R u b b l e Rock (> d i s t a n c e t o n e a r e s t ( 2 - 5 cm) (6-1 0 cm) (1 1-20 cm) (21-40 cm) 40 cm) 184 t h e same s i z e t o a v o i d p o s s i b l e c o m p l i c a t i o n s f r o m d i f f e r e n c e s i n m i c r o h a b i t a t u s e due t o v a r i a t i o n i n f i s h s i z e . A s i z e r a n g e o f 60-75 mm was c h o s e n b e c a u s e w i t h i n t h i s r a n g e s i z e - d e p e n d e n t m i c r o h a b i t a t v a r i a t i o n i s m i n o r ( E v e r e s t a n d Chapman 1 9 7 2 ) . F i s h s i z e s were e s t i m a t e d w h i l e s n o r k e l l i n g by c o m p a r i s o n w i t h a r e f e r e n c e r u l e . W a t e r t e m p e r a t u r e s i n a l l s t r e a m s were b e t w e e n o 16-18 C d u r i n g m i c r o h a b i t a t s u r v e y s . S t a t i s t i c a l a n a l y s i s B e c a u s e s t r e a m f i s h e s p r o b a b l y do n o t s e l e c t h a b i t a t s on t h e b a s i s o f s i n g l e a t t r i b u t e s a n d many f a c t o r s a p p e a r t o be r e l a t e d t o f i s h d i s t r i b u t i o n ( M o y l e a n d B a l t z 1985; Gro s s m a n a n d Freeman 1 9 8 7 ) , p r i n c i p a l c o m p o n e n t s a n a l y s i s o f t h e d a t a c o r r e l a t i o n m a t r i x was u s e d t o s u m m a r i z e v a r i a t i o n i n h a b i t a t u s e . A component s c o r e was t h e n c a l c u l a t e d f o r e a c h f i s h p o s i t i o n . S u b s e q u e n t a n a l y s e s o f mean s c o r e s i n v o l v e d a n a l y s i s o f v a r i a n c e f o r e a c h h a b i t a t a x i s a n d m u l t i v a r a t e a n a l y s i s o f v a r i a n c e f o r c o m b i n e d a x e s . P a i r w i s e c o m p a r i s o n s o f mean s c o r e s b e t w e e n s p e c i e s a n d p o p u l a t i o n s were c o n d u c t e d w i t h B o n f e r r o n i t e s t s ( D i x o n 1 9 8 6 ) . M u l t i v a r i a b l e r e l a t i o n s h i p s among t h e 2. v a r i o u s g r o u p s were s u m m a r i z e d by t h e M a h a l a n o b i s D . A l l c o m p u t a t i o n s f o l l o w Fox a n d G l u r e ( 1 9 7 6 ) , P i m e n t e l ( 1 9 7 9 ) , a n d D i x o n ( 1 9 8 6 ) . 185 R e s u l t s P r i n c i p a l c o m p o n e n t s a n a l y s i s o f t h e m i c r o h a b i t a t d a t a f o r b o t h 1985 a n d 1986 s u r v e y s a c c o u n t e d f o r a b o u t 7 5 % o f t h e t o t a l v a r i a b i l i t y i n t h r e e a x e s ( T a b l e 2 4 ) . F o r b o t h y e a r s , f o c a l w a t e r v e l o c i t y , maximum w a t e r v e l o c i t y , a n d s u b s t r a t e s i z e c o n t r i b u t e d most t o d i f f e r e n c e s i n m i c r o h a b i t a t s a l o n g t h e f i r s t c omponent a x i s (35 and 37% o f t o t a l v a r i a n c e r e s p e c t i v e l y ) . D u r i n g b o t h y e a r s , c o e f f i c i e n t s a l o n g t h e f i r s t a x i s were a l l p o s i t i v e i n d i c a t i n g i n c r e a s i n g m a g n i t u d e f o r a l l v a r i a b l e s . The s e c o n d a x i s f o r b o t h y e a r s s u g g e s t e d t h e i m p o r t a n c e o f w a t e r d e p t h a n d f i s h d e p t h a s f a c t o r s c o n t r i b u t i n g t o h a b i t a t v a r i a b i l i t y . W a t e r d e p t h a n d f i s h d e p t h m e a s u r e s ( n e g a t i v e s i g n s ) a p p e a r e d t o c o n t r a s t w i t h a l l o t h e r v a r i a b l e s ( p o s i t i v e s i g n s , e x c e p t f o r d i s t a n c e t o s h o r e - 1 9 8 6 ) . T h u s , t h e s e c o n d component a x i s s u g g e s t s a g r a d i e n t o f m i c r o h a b i t a t s f r o m d e e p , l o w v e l o c i t y w a t e r a r e a s c l o s e t o c o v e r a n d s h o r e w i t h s m a l l p a r t i c l e s u b s t r a t e s t o a r e a s o f s h a l l o w e r , f a s t e r w a t e r d i s t a n t f r o m s h o r e a n d c o v e r o b j e c t s w i t h p r e d o m i n a n t l y l a r g e r p a r t i c l e s u b s t r a t e s . The t h i r d a x i s was d i f f e r e n t i n t h e two y e a r s . I n 1985, maximum w a t e r v e l o c i t y c o n t r a s t e d w i t h d i s t a n c e t o c o v e r , b u t i n 1986 d i s t a n c e s t o c o v e r a n d t o s h o r e c o n t r a s t e d w i t h s u b s t r a t e s i z e a n d c o n t r i b u t e d most t o m i c r o h a b i t a t v a r i a t i o n . 186 Table 24. P r i n c i p a l components analysis of microhabitat use by juvenile chinook and coho salmon. Also indicated are the t o t a l variances contributed by each variable over the three axes. Variable c o e f f i c i e n t Component axis Total 1 2 3 Variance 1985 z 0.26 -0.64 0.10 83.8 Zb 0.06 -0.70 0.21 82.4 V 0.47 0.08 -0.12 75.9 Vmax 0.48 -0.03 -0.50 86.5 Zsh 0.40 0.24 0.39 70.2 Zcov 0.32 0.21 0.68 59. 1 Substr 0.46 0. 12 -0.25 52.7 Percent of var iance 35 23 15 73 1986 Z 0.28 -0.63 0.01 81.1 Zb 0.23 -0.67 0.11 81 .3 V 0.52 0.27 0.12 82.6 Vmax 0.52 0.28 0.14 83.2 Zsh 0.32 -0.04 -0.48 48.0 Zcov 0.26 0.07 -0.73 69.7 Substr 0.39 0.08 0.44 58.2 Percent of variance 37 22 15 74 187 F o l l o w i n g t h e m e t h o d o l o g y o f P i m e n t e l ( 1 9 7 9 , p. 6 7 ) , t h e v a r i a b l e s w h i c h c o n t r i b u t e d most t o m i c r o h a b i t a t v a r i a b i l i t y o v e r t h e f i r s t t h r e e a x e s a r e s u m m a r i z e d by t h e sum o f t h e v a r i a n c e s a c c o u n t e d f o r by e a c h . T h i s a n a l y s i s ( T a b l e 24) i n d i c a t e s t h a t o v e r a l l , t h e v a r i o u s w a t e r v e l o c i t y a n d w a t e r d e p t h m e a s u r e s were t h e most i m p o r t a n t d e t e r m i n a n t s o f m i c r o h a b i t a t v a r i a b i l i t y d u r i n g 1985 and 1986 (c_f. M o y l e and V o n d r a c e k 1 9 8 5 ) . I n 1985, S l i m C r e e k c h i n o o k w e re f o u n d i n m i c r o h a b i t a t s o f s l o w e r w a t e r v e l o c i t y , s h a l l o w e r w a t e r , c l o s e r t o s h o r e a n d c o v e r o b j e c t s , and o v e r s m a l l e r p a r t i c l e s u b s t r a t e s t h a n "random" p o s i t i o n s ( F i g . 26, PC 1, P < 0 . 0 0 1 ) . E a g l e R i v e r c h i n o o k were f o u n d a t m i c r o h a b i t a t s s i m i l a r t o random p o s i t i o n s a l o n g t h e f i r s t a x i s (P > 0 . 0 5 ) . By c o n t r a s t , E a g l e c o h o m i c r o h a b i t a t s were c h a r a c t e r i z e d by s l o w e r w a t e r v e l o c i t i e s , s h a l l o w e r w a t e r , g r e a t e r p r o x i m i t y t o c o v e r and s h o r e , a n d s m a l l e r p a r t i c l e s u b s t r a t e c l a s s e s t h a n a t random f o c a l p o i n t s ( F i g . 26, P < 0 . 0 0 1 ) . I n t h e E a g l e R i v e r , c h i n o o k s a l m o n were f o u n d a t g r e a t e r v a l u e s f o r a l l v a r i a b l e s t h a n c o h o a l o n g t h e f i r s t component a x i s (P < 0.001, F i g . 2 6 ) . The " m i c r o h a b i t a t s e p a r a t i o n " , h o w e v e r , b e t w e e n E a g l e c o h o and S l i m c h i n o o k was l e s s t h a n b e t w e e n c o h o a n d c h i n o o k i n s y m p a t r y i n t h e E a g l e R i v e r ( 0 . 8 5 v s 1.35, F i g . 2 6 ) . 188 F i g u r e 26. P l o t s of mean (+SE) p r i n c i p a l component scores summarizing m i c r o h a b i t a t use by j u v e n i l e coho and chinook salmon, 1985. COMPONENT AXIS 2 (23 % total var iance) 681 190 A l o n g PC a x i s 2, t h e r e were no d i f f e r e n c e s i n t h e m i c r o h a b i t a t f e a t u r e s o f random f o c a l p o i n t s a n d t h o s e o c c u p i e d by j u v e n i l e s ( a l l P > 0.05) n o r was t h e r e e v i d e n c e o f s i g n i f i c a n t m i c r o h a b i t a t d i f f e r e n c e s b e t w e e n s y m p a t r i c c o h o a n d c h i n o o k i n b o t h s t r e a m s (P > 0 . 1 ) . J u v e n i l e c h i n o o k i n s y m p a t r y , h o w e v e r , had l o w e r v a l u e s a l o n g PC2 ( i . e . g r e a t e r w a t e r d e p t h s ) t h a n S l i m C r e e k f i s h (P < 0.001, F i g . 2 6 ) . A l o n g t h e t h i r d component a x i s , no s i g n i f i c a n t m i c r o h a b i t a t d i f f e r e n c e s b e t w e e n s y m p a t r i c c o h o a n d c h i n o o k w e re d e t e c t e d ( P > 0 . 0 5 ) . E a g l e c o h o h a d h i g h e r PC3 v a l u e s ( h i g h e r maximum w a t e r v e l o c i t i e s , l a r g e r s u b s t r a t e s ) t h a n a t random p o s i t i o n s (P < 0 . 0 0 5 ) , b u t no d i f f e r e n c e s e x i s t e d b e t w e e n E a g l e c h i n o o k a nd random p o s i t i o n s (P > 0 . 0 5 ) . S l i m C r e e k c h i n o o k h a d a s i m i l a r d i s t r i b u t i o n t o random p o s i t i o n s a l o n g PC3 ( P > 0 . 0 5 ) . O v e r t h e f i r s t t h r e e component a x e s c o m b i n e d ( T a b l e 2 5 ) , m i c r o h a b i t a t u s e by E a g l e c o h o a n d c h i n o o k a n d c h i n o o k f r o m S l i m C r e e k were s i g n i f i c a n t l y d i f f e r e n t f r o m random m i c r o h a b i t a t s ( a l l P < 0 . 0 0 5 ) . M i c r o h a b i t a t u s e by s y m p a t r i c c o h o a n d c h i n o o k was d i f f e r e n t (D =0.79, P < 0 . 0 0 1 ) , b u t a l l o p a t r i c a n d s y m p a t r i c c h i n o o k were more s i m i l a r i n m i c r o h a b i t a t u s e t o e a c h o t h e r t h a n e i t h e r was t o c o h o (D =0.56). T h e r e was, h o w e v e r , a s m a l l e r d i f f e r e n c e b e t w e e n c o h o and S l i m ( a l l o p a t r i c ) c h i n o o k m i c r o h a b i t a t s t h a n b e t w e e n s y m p a t r i c c o h o and c h i n o o k (D =0.66 i v s D =0.79). I n 1986, m i c r o h a b i t a t s o f s y m p a t r i c c h i n o o k i n t h e E a g l e 191 T a b l e 25. M a t r i x o f M a h a l a n o b i s d i s t a n c e s among m i c r o h a b i t a t c e n t r o i d s f o r j u v e n i l e c h i n o o k a n d c o h o s a l m o n , 1985. V a l u e s a r e b a s e d on t h e f i r s t t h r e e component a x e s a nd a l l c o m p a r i s o n s a r e s i g n i f i c a n t a t P<0.001. E c = E a g l e c o h o , E c k = E a g l e c h i n o o k , E r = E a g l e random, S r = S l i m random, S c k = S l i m c h i n o o k . N Ec E c k E r S r S c k Ec 110 -Eck 1 22 0.79 E r 119 0.82 0.23 S r 115 1 .58 0.35 0.55 Sck 126 0.66 0.56 0.60 0.42 1 92 and Salmon r i v e r s were s i m i l a r t o random m i c r o h a b i t a t s ( P C 1 , P > 0 . 0 5 ) , b u t c h i n o o k f r o m S l i m a n d W a l k e r c r e e k s a n d c o h o f r o m E a g l e a n d Salmon r i v e r s u s e d m i c r o h a b i t a t s d i s t i n c t f r o m random m i c r o h a b i t a t s (P<0.001, F i g . 2 7 ) . As i n 1985, s y m p a t r i c c o h o a n d c h i n o o k u t i l i z e d d i f f e r e n t m i c r o h a b i t a t s ; c h i n o o k were f o u n d i n f a s t e r , more open w a t e r a r e a s t h a n c o h o (P< 0 . 0 0 1 ) . N o t a b l e m i c r o h a b i t a t d i f f e r e n c e s a l o n g PC 2 were b e t w e e n Salmon R i v e r c h i n o o k a n d c o h o ; S l i m a n d W a l k e r c h i n o o k a n d Salmon c h i n o o k a n d b e t w e e n b o t h p o p u l a t i o n s o f s y m p a t r i c c h i n o o k ( a l l P < 0.001, F i g . 2 7 ) . No s i g n i f i c a n t d i f f e r e n c e s i n m i c r o h a b i t a t s were e v i d e n t a l o n g PC 3. Ov e r t h e f i r s t t h r e e m i c r o h a b i t a t a x e s c o m b i n e d , c o h o a n d c h i n o o k f r o m a l l s t r e a m s u s e d a r e a s t h a t d i f f e r e d s i g n i f i c a n t l y f r o m random m i c r o h a b i t a t s , a n d s y m p a t r i c c o h o a n d c h i n o o k u s e d d i f f e r e n t m i c r o h a b i t a t s ( T a b l e 2 6 ) . I n f a c t , m i c r o h a b i t a t d i f f e r e n c e s b e t w e e n c o h o a n d c h i n o o k were s u c h t h a t , m i c r o h a b i t a t u s e by c h i n o o k i n t h e E a g l e R i v e r was more s i m i l a r t o m i c r o h a b i t a t u s e by c h i n o o k i n t h e Salmon R i v e r t h a n t o E a g l e R i v e r c o h o ( a n d v i c e v e r s a , T a b l e 2 6 ) . By, c o n t r a s t , a l l o p a t r i c c h i n o o k i n b o t h W a l k e r a n d S l i m c r e e k s were f o u n d i n m i c r o h a b i t a t s more s i m i l a r t o t h o s e o f c o h o t h a n t o t h o s e o f c h i n o o k f r o m t h e E a g l e o r Salmon r i v e r s ( T a b l e 2 6 ) . W h i l e t h e r e a r e g e n e r a l d i f f e r e n c e s i n m i c r o h a b i t a t u s e among v a r i o u s p o p u l a t i o n s o f c h i n o o k a n d c o h o , t h e r e was a l s o 193 F i g u r e 27. P l o t s o f mean (+SE) p r i n c i p a l component s c o r e s s u m m a r i z i n g m i c r o h a b i t a t u s e by j u v e n i l e c o h o a n d c h i n o o k s a l m o n , 1986. MICROHABITAT USE: 1986 H SALMON CHNK WALKER RANDOM — 0.5 H SLIM CHNK SLIM RANDOM EAGLE RANDOM WALKER CHNK SALMON RANDOM - 0 . 5 H _ s k _ l EAGLE CHNK EAGLE COHO SALMON COHO -1-I •1.5 r -1 0 -0.5 0.5 1 COMPONENT AXIS 1 (36 % total variance) 1.5 195 T a b l e 26. M a t r i x o f M a h a l a n o b i s d i s t a n c e s among m i c r o h a b i t a t c e n t r o i d s f o r j u v e n i l e c h i n o o k a nd c o h o s a l m o n , 1986. V a l u e s a r e b a s e d on t h e f i r s t t h r e e component a x e s a n d a l l c o m p a r i s o n s a r e s i g n i f i c a n t a t P<0.001. E c = E a g l e c o h o , E c k = E a g l e c h i n o o k , Samc=Salmon c o h o , Samck=Salmon c h i n o o k , S c k = S l i m c h i n o o k , Wck=Walker c h i n o o k . N Ec Eck Same Samck Sck Wck Ec 150 Eck 158 Same 156 Samck 150 Sck 180 Wck 166 2.49 0.15 1 .53 0.19 0.10 3.68 0.67 1.61 2.77 2.49 0.62 0.28 0.65 1 .75 0.30 196 c o n s i d e r a b l e v a r i a b i l i t y w i t h i n groups. For i n s t a n c e , c o n s i s t e n t i n t e r s p e c i f i c d i f f e r e n c e s i n m i c r o h a b i t a t use were evident along t r a n s e c t s with d i v e r s e c h a r a c t e r i s t i c s (e.g. r i f f l e s running i n t o p o o l s ) , but c o n s i d e r a b l e o v e r l a p i n m i c r o h a b i t a t use by sympatric s p e c i e s was observed i n more homogeneous h a b i t a t s (e.g. " r u n - l i k e " h a b i t a t s ) . In such h a b i t a t s , water v e l o c i t i e s and water depths occupied by coho and chinook were t y p i c a l l y i n t e r m e d i a t e to those a p p a r e n t l y p r e f e r r e d by each s p e c i e s . 197 3. EXPERIMENTAL INTRODUCTIONS OF J U V E N I L E COHO AND CHINOOK SALMON M e t h o d s E x p e r i m e n t a l a n i m a l s J u v e n i l e c o h o a n d c h i n o o k s a l m o n u s e d i n t h e e x p e r i m e n t a l i n t r o d u c t i o n s were i n c u b a t e d and r e a r e d i n t h e l a b o r a t o r y a t t h e U n i v e r s i t y . They were p r o g e n y f r o m c r o s s e s o f a number o f m a l e s a n d f e m a l e s f r o m S l i m C r e e k , E a g l e R i v e r , a nd B l a c k C r e e k a s d e s c r i b e d i n C h a p t e r 1. E x p e r i m e n t a l f a c i l i t y The e x p e r i m e n t a l s t r e a m was a F i s h e r i e s a n d O c e a n s Canada p i n k s a l m o n ( 0 . g o r b u s c h a ) s p a w n i n g c h a n n e l l o c a t e d n e a r Hope, B.C., a b o u t 150 km e a s t o f V a n c o u v e r ( F i g . 2 8 ) . The h i s t o r y , d e s i g n , a n d o p e r a t i o n o f t h e c o n t r o l l e d f l o w c h a n n e l i s d e t a i l e d by H o u r s t o n a n d M a c K i n n o n (1956) a n d F r a s e r a n d F e d o r e n k o ( 1 9 8 3 ) . J o n e s C r e e k c h a n n e l i s a p p r o x i m a t e l y 580 m l o n g , 5 m w i d e a n d c o n s i s t s o f s i x t e e n s e c t i o n s , e a c h 40 x 5 m ( F i g . 2 8 ) . E a c h s e c t i o n i s d e m a r k e d a t i t s d o w n s t r e a m end by " d r o p f a l l s " , c o n t r u c t e d f r o m r a i l w a y t i e s , w h i c h p r o v i d e a d r o p b e t w e e n a d j a c e n t s e c t i o n s o f 10 t o 30 cm. T h u s , e a c h s e c t i o n h a s a 198 F i g u r e 28. The J o n e s C r e e k s p a w n i n g c h a n n e l f a c i l i t y . . S P = s e t t l i n g p o n d s . E x p e r i m e n t s were c o n d u c t e d i n c h a n n e l s e c t i o n s 3, 4, and 5 and t h e a r r o w i n d i c a t e s d i r e c t i o n o f w a t e r f l o w . Redrawn f r o m F r a s e r a n d F e d o r e n k o ( 1 9 8 3 ) . 200 c o n t r o l l e d w a t e r d e p t h and v e l o c i t y . The g r a v e l w i t h i n e a c h s e c t i o n i s g r a d e d and b e t w e e n 4 a n d 6 cm i n d i a m e t e r . A c a n o p y o f d e c i d u o u s t r e e s a nd s a l m o n b e r r y c o v e r s a b o u t 90% o f t h e c h a n n e l l e n g t h . I n t a k e t o t h e c h a n n e l f r o m J o n e s C r e e k i s c o n t r o l l e d by a 1.0 m g a t e v a l v e ( F i g . 28) w h i c h d e l i v e r s w a t e r i n t o a 40 x 4 x 4 m s e t t l i n g p o n d a t t h e h e a d o f t h e c h a n n e l . The g a t e v a l v e was o p e n e d 3.5 wk b e f o r e e x p e r i m e n t s s t a r t e d t o a l l o w b e n t h i c i n v e r t e b r a t e s t o c o l o n i z e t h e s u b s t r a t e . E x p e r i m e n t s were r e s t r i c t e d t o t h r e e a d j a c e n t c h a n n e l s e c t i o n s ( N o s . 3, 4, a n d 5 a c c o r d i n g t o F i g . 28) w h i c h were s e l e c t e d f o r t h e i r g e n e r a l s i m i l a r i t y i n w a t e r d e p t h , w a t e r v e l o c i t y , a n d amount o f o v e r h e a d c o v e r . E a c h s e c t i o n was i s o l a t e d f r o m t h e s e c t i o n i m m e d i a t e l y up- a n d d o w n s t r e a m by f e n c e s o f 2.4 x 1.0 m p a n e l s a s o u t l i n e d i n C o l i n a n d T u t t y ( 1 9 7 9 ) . P a n e l s were c o n s t r u c t e d o f 5 x 8 cm wood f r a m e s o n t o w h i c h 0.6 cm w i r e s c r e e n i n g was f a s t e n e d . To f u r t h e r s u p p o r t t h e f e n c e p a n e l s and t o make them " f i s h - t i g h t " , a 1 m w i d e a p r o n o f p o l y e t h y l e n e s h e e t i n g was f i t t e d d o w n s t r e a m a l o n g t h e b o t t o m o f e a c h p a n e l a n d a n c h o r e d w i t h s a n d b a g s . Any f i s h m o v i n g d o w n s t r e a m i n t h e c h a n n e l s e c t i o n s w o u l d be d i r e c t e d a l o n g t h e p a n e l s a n d i n t o a t r o u g h w h i c h l e d t o a l i v e box ( 0 . 6 x 0.6 x 0.9 m). F e n c e s were p l a c e d s u c h t h a t e a c h s e c t i o n was 150 m i n a r e a (30 x 5 m). A g r i d o f b a i l e r t w i n e was s u s p e n d e d a l o n g t h e l e n g t h o f 201 e a c h s e c t i o n a t 20 cm i n t e r v a l s , 50 cm a b o v e t h e w a t e r s u r f a c e . T h i s g r i d p r e v e n t e d common m e r g a n s e r s , M e r g u s m e r g a n s e r , f r o m e n t e r i n g t h e c h a n n e l s e c t i o n s a n d p r e y i n g on i n t r o d u c e d s a l m o n . A t t h e d o w n s t r e a m end o f e x p e r i m e n t a l s e c t i o n No. 5, a s i m p l e W o l f t r a p ( W o l f 1950) was c o n s t r u c t e d t o e n u m e r a t e f i s h w h i c h may h a v e e s c a p e d u n d e r t h e f e n c e t r a p s i n e a c h s e c t i o n . The e x p e r i m e n t a l s t r e a m s e c t i o n s were c o n s i d e r e d t o be " f i s h t i g h t " b e c a u s e no f i s h were o b s e r v e d i n t h e W o l f t r a p n o r o u t s i d e t h e f e n c e t r a p s d u r i n g r e g u l a r u n d e r w a t e r s u r v e y s . E x p e r i m e n t a l d e s i g n a n d p r o t o c o l The p o t e n t i a l f o r i n t e r a c t i o n w i t h j u v e n i l e c o h o t o i n f l u e n c e h a b i t a t u s e a n d r e s i d e n c e t e n d e n c y o f c h i n o o k was e x a m i n e d by e x p e r i m e n t a l l y t e s t i n g t h r e e h y p o t h e s e s i n a 2 x 3 f a c t o r i a l d e s i g n : (1) c h i n o o k e m i g r a t i o n f r o m t h e e x p e r i m e n t a l s e c t i o n s when s t o c k e d w i t h c o h o s a l m o n i s s i m i l a r t o t h a t when c h i n o o k a r e s t o c k e d a l o n e , ( 2 ) c h i n o o k h a b i t a t u s e when s t o c k e d w i t h c o h o i s s i m i l a r t o t h a t when c h i n o o k a r e s t o c k e d a l o n e , a n d (3) c h i n o o k f r o m S l i m C r e e k ( a l l o p a t r i c ) a n d t h e E a g l e R i v e r ( s y m p a t r i c w i t h c o h o ) a r e s i m i l a r w i t h r e s p e c t t o (1) a n d (2) a b o v e . The e x p e r i m e n t c o n s i s t e d o f two l e v e l s o f a " c h i n o o k p o p u l a t i o n " f a c t o r ( S l i m a n d E a g l e c h i n o o k ) a n d t h r e e l e v e l s o f a " s p e c i e s i n t r o d u c t i o n " f a c t o r ( c h i n o o k i n t r o d u c e d a l o n e a t 1 f i s h / m ' , c h i n o o k p l u s c o h o e a c h i n t r o d u c e d a t 1 f i s h / m , a n d c h i n o o k i n t r o d u c e d a l o n e a t 2 f i s h / m . E a c h t r e a t m e n t c o m b i n a t i o n was r e p l i c a t e d f o u r t i m e s f o r a t o t a l o f 24 202 i n t r o d u c t i o n t r i a l s (2 p o p u l a t i o n s x 3 s p e c i e s i n t r o d u c t i o n t r e a t m e n t s x 4 r e p l i c a t i o n s e a c h ) . Mid-summer u n d e r w a t e r c e n s u s e s o f t h e t e s t p o p u l a t i o n s i n t h e i r n a t a l s t r e a m s a n d p i l o t i n t r o d u c t i o n s i n t h e s p a w n i n g c h a n n e l s u g g e s t e d t h a t Z i n i t i a l f i s h d e n s i t i e s o f 1-2 f i s h / m were a p p r o p r i a t e . Two d a y s b e f o r e an e x p e r i m e n t , f i s h were i s o l a t e d i n h o l d i n g t a n k s a t t h e U n i v e r s i t y , s t a r v e d f o r 24 h, a n d p l a c e d i n 75 1 b u c k e t s l i n e d w i t h p l a s t i c b a g s t h r e e - f i f t h s f i l l e d w i t h w a t e r . The f i s h were t r a n s p o r t e d t o t h e J o n e s C r e e k e x p e r i m e n t a l f a c i l i t y , h e l d i n t h e bags t o a l l o w t h e t e m p e r a t u r e t o r e a c h t h a t o f t h e c h a n n e l w a t e r ( a b o u t 0.5 h ) , a n d r e l e a s e d i n t o h o l d i n g c a g e s t o be h e l d o v e r n i g h t b e f o r e b e i n g f e d t h e n e x t m o r n i n g . The m o r n i n g a f t e r a r r i v a l a t J o n e s C r e e k , 50 f i s h were d i p n e t t e d f r o m t h e h o l d i n g c a g e s , m e a s u r e d ( F L ) , r e t u r n e d t o t h e h o l d i n g c a g e s a n d f e d o n c e . T w e n t y - f o u r h l a t e r , t h e y were i n t r o d u c e d t o q u i e t p o o l s i n e a c h e x p e r i m e n t a l s e c t i o n . J u v e n i l e s a l m o n i d s i n t r o d u c e d i n t o n o v e l h a b i t a t s o f t e n r e s p o n d i m m e d i a t e l y , o r w i t h i n a few h o u r s , by m i g r a t i n g d o w n s t r e a m ( J e n k i n s 1971; B i l b y a n d B i s s o n 1 9 8 7 ) . To m i n i m i z e t h e i n f l u e n c e o f t h e " n o v e l h a b i t a t " f a c t o r on f i s h b e h a v i o u r a n d h a b i t a t u s e , t h e t r a p s a t t h e end o f e a c h s e c t i o n were c l o s e d f o r t h e f i r s t 24 h a f t e r t h e f i s h were i n t r o d u c e d t o p r e v e n t them f r o m e m i g r a t i n g . A t 8:00 PM t h e f o l l o w i n g day a n d 8:00 AM, 12:00 Noon, a n d 8:00 PM f o r t h e n e x t 6 d, f i s h e n t e r i n g t h e 203 d o w n s t r e a m t r a p s were e n u m e r a t e d a n d m e a s u r e d ( F L ) . H a b i t a t u s e by j u v e n i l e c o h o a n d c h i n o o k was r e c o r d e d o v e r t h e t r i a l p e r i o d s by r e c o r d i n g t h e i r o c c u r r e n c e i n " p o o l " a n d " r i f f l e " s u b s e c t i o n s i n e a c h c h a n n e l s e c t i o n . T r a n s e c t s were e s t a b l i s h e d p e r p e n d i c u l a r t o t h e w a t e r f l o w e v e r y 5 m a l o n g t h e l e n g t h o f e a c h s e c t i o n . Water v e l o c i t y a n d w a t e r d e p t h were m e a s u r e d a l o n g t h e s e t r a n s e c t s u s i n g an O t t c u r r e n t m e t e r and a m e t e r s t i c k . B a s e d on t h e s e m e a s u r e m e n t s , s u b s e c t i o n s were s e l e c t e d i n e a c h s e c t i o n t o r e p r e s e n t " p o o l - " ( v e l o c i t i e s <15 cm/s) and " r i f f l e - l i k e " ( v e l o c i t i e s >25 cm/s) h a b i t a t s . P o o l s u b s e c t i o n s a l s o t e n d e d t o be d e e p e r t h a n r i f f l e s ( T a b l e 2 7 ) . W a t e r v e l o c i t y a n d w a t e r d e p t h were s e l e c t e d a s f a c t o r s t o be v a r i e d b e c a u s e o f t h e i r i m p o r t a n c e i n c o n t r i b u t i n g t o m i c r o h a b i t a t v a r i a b i l i t y o f w i l d s a l m o n ( T a b l e 2 4 ) . E i g h t s u b s e c t i o n s ( f o u r p o o l s a n d f o u r r i f f l e s , e a c h 1.5 x 1.5 m) i n e a c h e x p e r i m e n t a l s e c t i o n were m a r k e d by f l a g g i n g t h e i r c o r n e r s . P e r c e n t c o v e r was e s t i m a t e d by e y e a n d s u p p l e m e n t e d by t h e a d d i t i o n o f r o c k a n d wood o b j e c t s t o a maximum o f 30% o f t h e s u r f a c e a r e a i n p o o l h a b i t a t s . I n a l l r i f f l e s u b s e c t i o n s , r o c k a n d wood i n s t r e a m c o v e r was l e s s t h a n 30%. H a b i t a t u s e by c o h o and c h i n o o k was m o n i t o r e d by c o u n t i n g t h e number o f f i s h i n e a c h s u b s e c t i o n d u r i n g s n o r k e l c e n s u s e s . C e n s u s e s were c o n d u c t e d on d a y 2 a n d day 4 o f e a c h t r i a l a t 10:00 a n d 14:00 f o r a t o t a l o f f o u r r e p e a t e d c o u n t s p e r r e p l i c a t e . R e p e a t e d o b s e r v a t i o n s were u s e d t o a c c o u n t f o r 204 T a b l e 27. A v e r a g e w a t e r v e l o c i t i e s a nd w a t e r d e p t h s i n s u b s e c t i o n s o f J o n e s C r e e k e x p e r i m e n t a l s t r e a m s e c t i o n s . I n e a c h s e c t i o n , t h e v a l u e s a r e t h e means (SE) o f f o u r p o o l s a n d f o u r r i f f l e s . V e l o c i t i e s m e a s u r e d i n cm/s, d e p t h s m e a s u r e d i n cm. P h y s i c a l v a r i a b l e S t r e a m s e c t i o n P o o l R i f f l e V e l o c i t y 3 8.7 (2 .1 ) 22. 0 (1 .6) D e p t h 3 30.6 (2 .4) 24. 4 (2 .5) V e l o c i t y 4 8.3 (2 .2) 24. 2 (3 .6) D e p t h 4 35.3 (2 .5) 37. 4 (1 .4) V e l o c i t y 5 10.7 (2 .8) 26. 4 (2 .1 ) D e p t h 5 32.1 (1 .7) 26. 2 (1 .5) 205 v o l a t i l i t y o f h a b i t a t u s e by t h e s a l m o n . D u r i n g e a c h c e n s u s and f o r 1 h t h e r e a f t e r , t h e d o w n s t r e a m t r a p s were c l o s e d so t h a t f i s h c o u l d n o t e m i g r a t e . A t t h e e n d o f e a c h t r i a l a f i n a l c e n s u s was c o n d u c t e d t o d e t e r m i n e t h e number o f f i s h r e m a i n i n g i n e a c h s e c t i o n . The c h a n n e l was t h e n d r a i n e d by c l o s i n g t h e i n t a k e v a l v e a n d a l l f i s h r e m a i n i n g i n t h e c h a n n e l were e n u m e r a t e d a n d p r e s e r v e d . F i n a l c e n s u s c o u n t s , o r t h e number o f f i s h c o l l e c t e d when t h e s e c t i o n s w e r e d r a i n e d ( w h i c h e v e r was g r e a t e r ) , p l u s t h e number o f f i s h e n u m e r a t e d i n t h e t r a p s were u s e d t o e s t i m a t e " f i s h l o s s " f r o m t h e s e c t i o n s . An a v e r a g e o f 7.7 (+0.94 SE) % o f i n i t i a l f i s h i n t r o d u c e d were u n a c c o u n t e d f o r a t t h e end o f e a c h t r i a l ( r a n g e 0 - 2 0 % ) . G r a v e l s i z e ( 4 - 6 cm d i a m e t e r ) was s u c h t h a t many f i s h were a b l e t o p e n e t r a t e t h e g r a v e l a s t h e c h a n n e l d r a i n e d m a k i n g t h e i r r e c o v e r y d i f f i c u l t . " U n a c c o u n t e d f o r " f i s h w ere most l i k e l y l o s t w i t h i n t h e c h a n n e l s u b s t r a t e r a t h e r t h a n t h r o u g h e s c a p e o r p r e d a t i o n . W a t e r t e m p e r a t u r e s d u r i n g t h e e x p e r i m e n t s r a n g e d f r o m a d a i l y a v e r a g e o f a b o u t 9 C i n mid-May t o 15 C i n J u l y . W h i l e i n t h e c h a n n e l , e x p e r i m e n t a l p o p u l a t i o n s o f s a l m o n f e d on n a t u r a l d r i f t . O v e r n i g h t d r i f t s a m p l e s i n d i c a t e d t h e p r e s e n c e o f l a r v a l m a y f l i e s , E p h e m e r e l l a s p p . , E p e o r u s , a n d B a e t i s , s t o n e f l i e s , C h l o r o p e r l a , a n d s m a l l e r numbers o f c a d d i s f l i e s , L e p i d o s t o m a . S a lmon were a l s o o b s e r v e d t o f e e d h e a v i l y a t d u s k on a d u l t i n s e c t s d r i f t i n g on the. w a t e r s u r f a c e . 206 C h i n o o k a n d c o h o s a l m o n were s o r t e d t o be o f s i m i l a r s i z e f o r t h e e x p e r i m e n t s . F o r t h e e i g h t r e p l i c a t e s when c o h o a n d c h i n o o k were i n t r o d u c e d t o g e t h e r , h o w e v e r , c h i n o o k were s l i g h t l y l a r g e r ; S l i m c h i n o o k a v e r a g e d (+SE, F L ) 65.4+0.51 mm, E a g l e c h i n o o k 64.5+0.74 mm, and c o h o 62.5+1.1 mm. To e s t a b l i s h what i n f l u e n c e t h e s e s m a l l d i f f e r e n c e s i n f i s h s i z e may h a v e h a d on h a b i t a t u s e , t h r e e p i l o t i n t r o d u c t i o n s o f 150 f i s h e a c h (two w i t h c h i n o o k , one w i t h c o h o ) were p e r f o r m e d . F o r e a c h , f i s h were g r a d e d i n t o 7 s i z e c l a s s e s ( F L , mm): 5 8 - 5 9 , 6 0 - 6 1 , 6 2 - 6 3 , 6 4 - 6 5 , 66-67, 6 8 - 6 9 , a n d 70-72 w h i c h c o v e r e d t h e c o m p l e t e s i z e r a n g e o f f i s h u s e d i n t h e e x p e r i m e n t s . F i s h i n e a c h s i z e c l a s s were i d e n t i f i e d by c o l d b r a n d s a p p l i e d a t d i s t i n c t i v e body p o s i t i o n s u s i n g l i q u i d n i t r o g e n . A f t e r a l l o w i n g t h e f i s h t o a d j u s t t o t h e c h a n n e l f o r 2 d, I r e c o r d e d t h e p o s i t i o n s o f a l l f i s h w i t h i n a i m p a t h t h r o u g h t h e m i d d l e o f t h e c h a n n e l . W a t e r v e l o c i t y a n d w a t e r d e p t h were r e c o r d e d f o r e a c h p o s i t i o n a n d c o m p a r e d w i t h t h e known l e n g t h ( s i z e c a t e g o r y m i d - p o i n t ) o f f i s h o c c u p y i n g s p e c i f i c p o s i t i o n s . I n t h e s e i n t r o d u c t i o n s . , body s i z e was u n r e l a t e d t o e i t h e r w a t e r v e l o c i t y o r w a t e r d e p t h o c c u p i e d ( e . g . F i g . 29, r ' s r a n g e d b e t w e e n -0.12 a n d 0.16, f o r 40 < n < 50, a l l P > 0 . 0 5 ) . S m a l l s i z e v a r i a t i o n b e t w e e n t h e e x p e r i m e n t a l g r o u p s o f s a l m o n was, t h e r e f o r e , c o n c l u d e d n o t t o be a f a c t o r c o n f o u n d i n g i n t e r p r e t a t i o n o f a n y s u b s e q u e n t d i f f e r e n c e s i n h a b i t a t u s e . F i g u r e 29. R e l a t i o n s h i p between f i s h s i z e and water v e l o c i of m i c r o h a b i t a t s occupied. The data are from a t r i a l u s i n g S l i m Creek chinook. FOCAL POINT VELOCITY (cm/s ) _ _ M M <^ o cn o cn o on o cn CD CD 802 209 S t a t i s t i c a l a n a l y s i s E m i g r a t i o n t e n d e n c y was e x p r e s s e d a s t h e p r o p o r t i o n o f c h i n o o k e n t e r i n g t h e d o w n s t r e a m t r a p s o v e r t h e 6 d t r i a l s . T h e s e d a t a were a r c s i n e s q u a r e - r o o t t r a n s f o r m e d a n d f a c t o r i a l a n a l y s i s o f v a r i a n c e was p e r f o r m e d ; s p e c i e s i n t r o d u c t i o n t r e a t m e n t a n d c h i n o o k p o p u l a t i o n were t h e m a i n e f f e c t s . When a l l f i s h i n i t i a l l y i n t r o d u c e d were d e n i e d e m i g r a t i o n , i s o l a t e d s h o a l s o f f i s h (10-40 i n number) were o f t e n o b s e r v e d " r o a m i n g " a b o u t t h e e x p e r i m e n t a l s e c t i o n s . H a b i t a t c h a r a c t e r i z a t i o n of s u c h g r o u p s was p r o b l e m a t i c s i n c e t h e y t e n d e d t o d r i f t i n a n d o u t o f s u b s e c t i o n s and t o d i s p l a c e f i s h h o l d i n g p o s i t i o n s i n s u b s e c t i o n s . R e s t r i c t i o n s on t h e amount o f t i m e t h a t t h e c h a n n e l was a v a i l a b l e f o r e x p e r i m e n t s , a n d o f f i s h number, p r e v e n t e d s e p a r a t e e x p e r i m e n t s b e i n g p e r f o r m e d f o r e m i g r a t i o n a n d h a b i t a t u s e . T h e r e f o r e , h a b i t a t use was m o n i t o r e d when f i s h w ere f r e e t o e m i g r a t e , a n d t h u s i n i t i a l f i s h d e n s i t i e s c h a n g e d o v e r t h e c o u r s e o f t h e o b s e r v a t i o n s . R e p e a t e d m e a s u r e s a n a l y s i s o f c o v a r i a n c e was u s e d t o t e s t f o r d i f f e r e n c e s i n t h e number o f c h i n o o k i n p o o l a n d r i f f l e h a b i t a t s s e p a r a t e l y . The t o t a l number o f f i s h c o u n t e d d u r i n g e a c h c e n s u s ( a s a m e a s u r e o f d e n s i t y ) was t h e c o v a r i a t e , s p e c i e s i n t r o d u c t i o n t r e a t m e n t and c h i n o o k p o p u l a t i o n were t h e m a i n e f f e c t s , a n d o b s e r v a t i o n day a n d p e r i o d were t h e r e p e a t e d m e a s u r e s . H o m o g e n e i t y o f c o v a r i a t e s l o p e s was c o n f i r m e d among t r e a t m e n t g r o u p s a n d a p o s t e r i o r i t e s t s f o l l o w e d T u k e y ' s p r o c e d u r e . 210 R e s u l t s I n i t i a l b e h a v i o u r Upon i n t r o d u c t i o n , j u v e n i l e c o h o a n d c h i n o o k r e a c t e d by s e e k i n g c o v e r u n d e r l a r g e r o c k s o r v e g e t a t i o n o v e r h a n g i n g t h e c h a n n e l m a r g i n s . O t h e r s , i n a g g r e g a t i o n s o f 2 0 - 4 0 , moved d o w n s t r e a m t o n e a r t h e t r a p o p e n i n g s w i t h i n 1-2 m i n . L a r g e numbers o f s a l m o n c o u l d be s e e n h o l d i n g p o s i t i o n s u p s t r e a m o f t h e t r a p o p e n i n g s a n d f e n c e p a n e l s . W i t h i n 1 h f i s h g r a d u a l l y moved u p s t r e a m t o t a k e up p o s i t i o n s i n t h e m i d d l e a n d u p p e r p o r t i o n s o f t h e c h a n n e l s e c t i o n s . A f t e r 2-3 h few f i s h were o b s e r v e d j u s t u p s t r e a m o f t h e f e n c e p a n e l s ; r a t h e r i n d i v i d u a l s c o u l d be s e e n s c a t t e r e d t h r o u g h o u t t h e s e c t i o n s o f t e n r i s i n g t o t h e s u r f a c e t o s t r i k e a t o b j e c t s f l o a t i n g d o w n s t r e a m a n d i n t e r a c t i n g w i t h one a n o t h e r . E m i g r a t i o n f r o m t h e c h a n n e l An a v e r a g e 4 1 % o f c h i n o o k e m i g r a t e d f r o m t h e e x p e r i m e n t a l s e c t i o n s o v e r t h e c o u r s e o f t h e s t u d y when i n t r o d u c e d a l o n e a t 1 f i s h / m . M o s t e m i g r a t i n g f i s h e n t e r e d t h e t r a p s d u r i n g t h e f i r s t 3 d i n a n y one t r i a l ( F i g . 3 0 ) . E a g l e a n d S l i m c h i n o o k e x h i b i t e d s i m i l a r e m i g r a t i o n t e n d e n c y when i n t r o d u c e d a l o n e ( S l i m x= 4 1 . 5 % , E a g l e x = 4 0 . 5 % ) . S i x t y - o n e p e r c e n t o f c h i n o o k e m i g r a t e d f r o m t h e c h a n n e l s e c t i o n s when i n t r o d u c e d w i t h an X e q u a l number o f c o h o a t 2 f i s h / m ; a h i g h e r p e r c e n t a g e o f S l i m 21 1 F i g u r e 30. Temporal changes i n mean (+SE) p r o p o r t i o n of t o t a l e m i g r a t i o n by j u v e n i l e salmon i n the experimental stream s e c t i o n s . Values were c a l c u l a t e d from i n d i v i d u a l t r i a l s pooled a c r o s s s p e c i e s and treatment (N=32). 212 CDlVaBrNflNB 1V101 JO NOIldOdOcJd NV3kN 213 C r e e k f i s h e m i g r a t e d (x=67%) c o m p a r e d t o E a g l e R i v e r c h i n o o k (x=55%, F i g . 3 2 ) . An i n t e r m e d i a t e p e r c e n t a g e o f i n i t i a l c h i n o o k numbers e m i g r a t e d f r o m t h e c h a n n e l s e c t i o n s (x=49%) when t h e y were i n t r o d u c e d a l o n e a t 2 f i s h / m , S l i m c h i n o o k a g a i n showed a s l i g h t l y g r e a t e r t e n d e n c y t o e m i g r a t e t h a n E a g l e c h i n o o k (x=55 a n d 4 9 % r e s p e c t i v e l y ) . Mean s i z e s f o r i n i t i a l a n d e m i g r a n t f i s h were a v a i l a b l e f o r 12 o f t h e 24 i n t r o d u c t i o n t r i a l s ; e m i g r a n t s were o f t e n s m a l l e r t h a n t h e mean s i z e o f f i s h i n i t i a l l y i n t r o d u c e d , b u t t h e r e were no s i g n i f i c a n t d i f f e r e n c e s ( B o n f e r r o n i - a d j u s t e d t - t e s t s , a l l P>0.01, F i g . 3 1 ) . O v e r a l l , t h e r e was no i n f l u e n c e o f s p e c i e s i n t r o d u c t i o n t r e a t m e n t on t h e p e r c e n t a g e o f i n i t i a l c h i n o o k numbers w h i c h e m i g r a t e d ( d f = 2 , l 8 , P = 0 . 0 8 3 ) . T h e r e was a l s o no d i f f e r e n c e , i n e m i g r a t i o n t e n d e n c y b e t w e e n S l i m a n d E a g l e c h i n o o k e i t h e r o v e r a l l ( d f = 1 , 1 8 , P = 0 . 2 4 ) , o r i n r e s p o n s e t o t h e s p e c i e s i n t r o d u c t i o n t r e a t m e n t s ( d f = 2 , l 8 , s p e c i e s i n t r o d u c t i o n X p o p u l a t i o n P = 0 . 7 6 ) . By c o n t r a s t t o t h e e x t e n s i v e movement by c h i n o o k s a l m o n , an a v e r a g e o f o n l y 14+3.9 (SE) % o f i n i t i a l c o h o numbers e n t e r e d t h e t r a p s . H a b i t a t u s e I n t h e e x p e r i m e n t a l s t r e a m s e c t i o n s c o h o a n d c h i n o o k s a l m o n u s e d d i f f e r e n t h a b i t a t s . C h i n o o k were much more l i k e l y t o be 214 F i g u r e 31. Mean (+SE) s i z e s o f i n i t i a l a n d e m i g r a n t s a l m o n j u v e n i l e s . 3 1 a = S l i m C r e e k r e p l i c a t e 2, 3 1 b = E a g l e R i v e r r e p l i c a t e 4. MEAN (±SE) FORK LENGTH (mm) tO -t»- CD CO o o o o o 0-4 6" MEAN (±SE) FORK LENGTH ( m m ) r o cn co o o o o o o o o o O O I I HO HO ONI ONI Le PI r INIT OK OK CQ CD o JO > lAL EMI INIT nd 9U NTS ' GRANTS > r~ 216 gure 32. Mean (+SE) p r o p o r t i o n emigration from experimental channel s e c t i o n s by chinook when int r o d u c e d alone and with coho salmon. JONES CREEK CHINOOK EMIGRATION EXPERIMENT O.8-1 TREATMENT 218 f o u n d i n r i f f l e h a b i t a t s w h i l e c o h o were f o u n d a l m o s t e x c l u s i v e l y i n t h e p o o l h a b i t a t s , a d i f f e r e n c e c o n s i s t e n t w i t h t h a t o b s e r v e d i n t h e w i l d ( F i g . 3 3 ) . D i f f e r e n t i a l h a b i t a t u se a p p e a r e d t o o c c u r r a p i d l y ; o b s e r v a t i o n s f r o m t h e s t r e a m b a n k s i n d i c a t e d t h a t c o h o were i n p o o l s and c h i n o o k i n r i f f l e s w i t h i n 1 d o f i n t r o d u c t i o n . The number o f c h i n o o k i n p o o l h a b i t a t s v a r i e d s i g n i f i c a n t l y among t h e t r e a t m e n t s ( d f = 2 , 1 4 ; P=0.001, T a b l e 2 8 ) . Fewer c h i n o o k were f o u n d i n t h e p o o l h a b i t a t s when i n t r o d u c e d w i t h 2 c o h o t h a n when i n t r o d u c e d a l o n e a t 1 f i s h / m (P<0.05, T a b l e 2 8 ) , 2. b u t n o t a t 2 f i s h / m ( P > 0 . 0 5 ) . More S l i m f i s h were c o u n t e d i n p o o l h a b i t a t s t h a n E a g l e c h i n o o k , b u t t h i s d i f f e r e n c e was n o t s i g n i f i c a n t ( T a b l e 2 8 , d f = 1 , 1 4 ; P = 0 . 0 9 ) . B o t h p o p u l a t i o n s r e s p o n d e d by d e c r e a s i n g t h e i r numbers i n p o o l h a b i t a t s when i n t r o d u c e d w i t h c o h o a l t h o u g h t h i s e f f e c t was p e r h a p s s l i g h t l y s t r o n g e r f o r S l i m c h i n o o k ( s p e c i e s i n t r o d u c t i o n t r e a t m e n t x p o p u l a t i o n , P=0.06, d f = 2 , 1 4 ) . The numbers o f c h i n o o k i n p o o l s was s t a b l e b o t h o v e r o b s e r v a t i o n p e r i o d s a n d d a y s ( b o t h r e p e a t e d f a c t o r s P > 0 . 1 ) . Use o f r i f f l e s by c h i n o o k was a l s o i n f l u e n c e d by s p e c i e s i n t r o d u c t i o n t r e a t m e n t (P<0.01, T a b l e 2 9 ) ; more f i s h u s e d r i f f l e s when i n t r o d u c e d w i t h c o h o . E a g l e a n d S l i m c h i n o o k d i d n o t d i f f e r s i g n i f i c a n t l y i n o v e r a l l u se o f r i f f l e h a b i t a t s ( T a b l e 29, d f = 1 , 1 4 ; P = 0 . 2 3 ) . A l t h o u g h c o - i n t r o d u c t i o n w i t h c o h o a l t e r e d numbers o f c h i n o o k i n p o o l and r i f f l e h a b i t a t s , c h i n o o k 219 F i g u r e 33. R e l a t i v e u s e o f p o o l a n d r i f f l e h a b i t a t s i n J o n e s C r e e k e x p e r i m e n t a l s t r e a m s e c t i o n s by c o h o a n d c h i n o o k s a l m o n . JONES CREEK HABITAT USE: CHINOOK AND COHO 1-1 221 T a b l e 28. Number (mean+SE) o f c h i n o o k f o u n d i n p o o l h a b i t a t s i n J o n e s C r e e k . T r e a t m e n t 1 = c h i n o o k i n i t i a l d e n s i t y 1 f i s h / m 2 , 2 = c h i n o o k a nd c o h o a t 2 f i s h / m z , 3 = c h i n o o k a t 2 f i s h / m 2 " . C h i n o o k p o p u l a t i o n S l i m C r e e k E a g l e R i v e r Mean N 4 4 8 I n t r o d u c t i o n T r e a t m e n t N 1 4 26.7 ( 2 . 3 ) 21.6 ( 2 . 1 ) 24.0 (1 .5) 2 4 13.2 ( 2 . 2 ) 16.6 ( 2 . 1 ) 14.3 (1 .6) 3 4 21.8 ( 2 . 2 ) 16.2 ( 2 . 5 ) 22.4 (1 .7) Mean 12 21.6 ( 1 . 3 ) 18.1 ( 1 . 3 ) 19.8 (1 .4) 222 T a b l e 29. Number (+SE) o f c h i n o o k f o u n d i n r i f f l e h a b i t a t s i n J o n e s C r e e k . T r e a t m e n t 1 = c h i n o o k i n i t i a l d e n s i t y 1 f i s h / m " 1 , 2 = c h i n o o k a n d c o h o a t 2 f i s h / m z , 3 = c h i n o o k a t 2 f i s h / m z . C h i n o o k p o p u l a t i o n S l i m C r e e k E a g l e R i v e r Mean N 4 4 8 I n t r o d u c t i o n T r e a t m e n t N 1 4 32.3 ( 2 . 5 ) 37.6 ( 2 . 1 ) 35.2 (1 .5) 2 4 43.4 ( 2 . 2 ) 42.5 ( 2 . 1 ) 42.8 (1 .6) 3 4 37.4 ( 2 . 1 ) 43.0 ( 2 . 5 ) 40.1 (1 .7) Mean 1 2 37.6 ( 1 . 3 ) 41.2 ( 1 . 3 ) 39.4 (3 .7) 223 were more numerous i n r i f f l e s t h a n i n p o o l s (same t o t a l s u r f a c e a r e a ) r e g a r d l e s s o f w h e t h e r t h e y were i n t r o d u c e d a l o n e o r w i t h c o h o ( T a b l e s 28, 2 9 ) . T h e r e f o r e , c h i n o o k a p p a r e n t l y p r e f e r r e d r i f f l e s o v e r p o o l s a n d i n t r o d u c t i o n w i t h c o h o o n l y e n h a n c e d t h i s p r e f e r e n c e . D i s c u s s i o n I f b e h a v i o u r a l i n t e r a c t i o n w i t h c o h o s a l m o n i n f l u e n c e s d u r a t i o n o f f r e s h w a t e r r e s i d e n c e by c h i n o o k s e v e r a l r e s u l t s were e x p e c t e d . F i r s t , i n numerous c a s e s i n w h i c h one s p e c i e s a p p e a r s t o i n f l u e n c e t h e d i s t r i b u t i o n o r a b u n d a n c e of a n o t h e r t h e a f f e c t e d s p e c i e s i s u s u a l l y s u b o r d i n a t e ( S h e p p a r d 1971; M o r s e 1974; Werner and H a l l 1977; S c h o e n e r 1983; N i s h i k a w a 1985; E b e r s o l e 1 9 8 6 ) . I n t h e p r e s e n t c o n t e x t , c o h o s h o u l d s o c i a l l y d o m i n a t e c h i n o o k i f , t h r o u g h d i r e c t a g g r e s s i o n , t h e y i n f l u e n c e f r e s h w a t e r r e s i d e n c e by c h i n o o k . T h i s e x p e c t a t i o n was r e a l i z e d i n t h e l a b o r a t o r y s t r e a m t a n k s ; n e w l y - e m e r g e d c o h o were d e s p o t i c o v e r c h i n o o k a l t h o u g h s u c h d o m i n a t i o n d i d n o t a p p e a r t o be u n i f o r m a c r o s s c h i n o o k p o p u l a t i o n s ( F i g . 2 5 ) . B e h a v i o u r a l d o m i n a t i o n o f c h i n o o k by c o h o i s c o n s i s t e n t w i t h t h e r e s u l t s o f S t e i n e t a l . ( 1 9 7 2 ) who showed t h a t i n t h e S i x e s R i v e r ( O r e g o n ) c o h o s o c i a l l y d o m i n a t e d c h i n o o k . I n b o t h t h e work o f S t e i n e t a l . a n d t h e p r e s e n t s t u d y , c o h o t e n d e d n o t 224 o n l y t o d i r e c t more a t t a c k s a t c h i n o o k t h a n v i c e v e r s a , b u t a l s o t o d o m i n a t e u p s t r e a m a r e a s o f e x p e r i m e n t a l t a n k s where f o o d was i n t r o d u c e d . S t e i n e t a l . ( 1 9 7 2) f o u n d t h a t c o h o grew f a s t e r t h a n c h i n o o k a n d s u p p r e s s e d t h e i r g r o w t h r a t e s , a r e s u l t t h a t t h e y c o n c l u d e d was a d i r e c t c o n s e q u e n c e o f t h e b e h a v i o u r a l s u b o r d i n a t i o n o f c h i n o o k . The b e h a v i o u r a l d o m i n a t i o n o f c h i n o o k by c o h o i s c o n s i s t e n t w i t h s t u d i e s t h a t h a v e r e p o r t e d t h a t c o h o d o m i n a t e s e v e r a l s a l m o n i d s ( H a r t m a n 1965; A l l e e 1982; F a u s c h a n d W h i t e 1986; G l o v a 1 9 8 6 ) . A t l e a s t i n c o n t r i v e d s i t u a t i o n s , t h e n , c o h o a r e a b l e t o d o m i n a t e c h i n o o k a n d i n f l u e n c e t h e i r d i s t r i b u t i o n s . The l i m i t e d g r o w t h d a t a r e p o r t e d by S t e i n e t a l . ( 1 9 7 2 ) a l s o s u g g e s t t h a t some a d v a n t a g e s i n t e r m s o f g r o w t h may a c c r u e t o i n d i v i d u a l c h i n o o k t h a t a v o i d , o r d i s p e r s e f r o m , m i c r o h a b i t a t s o c c u p i e d by c o h o . The a v a i l a b i l i t y o f s u i t a b l e h a b i t a t s i s an i m p o r t a n t d e t e r m i n a n t o f t h e s i z e a n d d i s t r i b u t i o n o f f i s h p o p u l a t i o n s (Chapman 1966; A l l e n 1969; M u n d i e 1974; Gorman a n d K a r r 1978; S c h l o s s e r 1982; Newman a n d W a t e r s 1 9 8 9 ) . T h e r e f o r e , i f b e h a v i o u r a l i n t e r a c t i o n w i t h c o h o i n f l u e n c e s d u r a t i o n o f f r e s h w a t e r r e s i d e n c e by c h i n o o k t h e n t h e s e c o n d e x p e c t a t i o n was t h a t c o h o w o u l d i n f l u e n c e some c o r r e l a t e o f f r e s h w a t e r r e s i d e n c e s u c h a s h a b i t a t u s e . M i c r o h a b i t a t u s e by a l l o p a t r i c a n d s y m p a t r i c c h i n o o k p r o v i d e d s u p p o r t f o r t h i s e x p e c t a t i o n . Coho a n d c h i n o o k u s e d d i f f e r e n t m i c r o h a b i t a t s when t o g e t h e r , b u t 225 c h i n o o k u t i l i z e d " c o h o - l i k e " p o o l h a b i t a t s t o a g r e a t e r e x t e n t when c o h o were a b s e n t ( F i g . 26, 2 7 ) . G i v e n t h e b e h a v i o u r a l d o m i n a n c e o f c o h o o v e r c h i n o o k , a p l a u s i b l e e x p l a n a t i o n i s t h a t i n t e r s p e c i f i c i n t e r a c t i o n i n s y m p a t r y p r o m o t e s d i f f e r e n t i a l m i c r o h a b i t a t u s e . D i f f e r e n c e s i n h a b i t a t u s e b e t w e e n c h i n o o k p o p u l a t i o n s , p a r t i c u l a r l y t h e u s e o f p o o l , " c o h o - l i k e " h a b i t a t s by c h i n o o k i n s t r e a m s w i t h o u t c o h o , i s c o n s i s t e n t w i t h t h i s e x p l a n a t i o n . S u c h an i n t e r p r e t a t i o n o f t h e d a t a i s n o t w i t h o u t d i f f i c u l t i e s . F i r s t , some u n c o n t r o l l e d a n d u n m e a s u r e d v a r i a b l e ( s ) t h a t c o - v a r y w i t h t h e p r e s e n c e o r a b s e n c e o f c o h o s a l m o n a nd t h a t i n f l u e n c e h a b i t a t u s e m i g h t d i f f e r among t h e s t u d y p o p u l a t i o n s ( C o n n e l l 1983; Diamond 1986; F a u s c h 1 9 8 8 ) . The a b u n d a n c e a n d d i s t r i b u t i o n o f f o o d a n d p r e d a t o r s may i n f l u e n c e h a b i t a t u s e i n f i s h e s (Chapman a n d B j o r n n 1969; E v e r e s t a n d Chapman 1972; W e r n e r e t a l . 1983; Power 1984; H a r v e y e t a l . 1988) a n d were u n c o n t r o l l e d i n t h i s s t u d y . H owever, b e c a u s e t h e h a b i t a t u s e r e s u l t s w e r e c o n s i s t e n t b e t w e e n y e a r s a n d a c r o s s " t r e a t m e n t " p o p u l a t i o n s , u n c o n t r o l l e d v a r i a t i o n was p r o b a b l y n o t a c o n f o u n d i n g f a c t o r i n my s t u d y . A s e c o n d l i m i t a t i o n was t h a t f i e l d p o p u l a t i o n s were n o t m a n i p u l a t e d . T h e r e f o r e , a p l a u s i b l e a l t e r n a t i v e e x p l a n a t i o n f o r t h e r e s u l t s i s t h a t d i f f e r e n c e s i n m i c r o h a b i t a t u s e r e s u l t f r o m g e n e t i c d i f f e r e n c e s i n h a b i t a t p r e f e r e n c e b e t w e e n c o h o a nd c h i n o o k a n d b e t w e e n S l i m a n d E a g l e c h i n o o k ( C o l w e l l a n d F u e n t e s 226 1975; F a u s c h 1 9 8 8 ) . The v a r i o u s s p e c i e s o f O n c o r h y n c h u s d i f f e r i n a v a r i e t y o f b e h a v i o u r a l , p h y s i o l o g i c a l , a n d m o r p h o l o g i c a l t r a i t s ( B r e t t 1952; H i k i t a 1962; W e i s b a r t 1968; H oar 1976) w h i c h s u g g e s t s t h a t t h e y m i g h t d i f f e r i n h a b i t a t p r e f e r e n c e a s w e l l . I f t h e d i f f e r e n c e s a r e i n d e e d g e n e t i c , t h e n t h e y m i g h t be t h e r e s u l t o f p a s t s e l e c t i o n f r o m i n t e r s p e c i f i c i n t e r a c t i o n a c t i n g t o f a v o u r i n d i v i d u a l s f r o m b o t h s p e c i e s w h i c h s o u g h t t o r e d u c e t h e c o s t s o f i n t e r s p e c i f i c a g g r e s s i o n by u s i n g a l t e r n a t i v e h a b i t a t s . P r e s e n t b e h a v i o u r a l i n t e r a c t i o n may a c t o n l y t o r e i n f o r c e d i f f e r e n c e s i n h a b i t a t p r e f e r e n c e . A l t e r n a t i v e l y , e v o l u t i o n o f d i f f e r e n c e s i n h a b i t a t p r e f e r e n c e d u r i n g a l l o p a t r i c d i v e r g e n c e o f c o h o and c h i n o o k f r o m a common a n c e s t o r c o u l d a l s o a c c o u n t f o r d i f f e r e n c e s o b s e r v e d d u r i n g s e c o n d a r y c o n t a c t . U n f o r t u n a t e l y , t h e h i s t o r i c a l n a t u r e o f t h e s e a l t e r n a t i v e e x p l a n a t i o n s makes t h e i r r e s o l u t i o n d i f f i c u l t ( E n d l e r 1982; C o n n e l l 1 9 8 3 ) . Numerous i n v e s t i g a t i o n s i n v o l v i n g b o t h f i e l d a n d l a b o r a t o r y s t u d i e s o f b e h a v i o u r a l i n t e r a c t i o n s and h a b i t a t u s e h a v e been c o n d u c t e d on s y m p a t r i c f i s h s p e c i e s ( e . g . E b e r s o l e 1986; H e a r n a n d K y n a r d 1986; R o s s 1 9 8 7 ) . S t u d i e s o f f i s h i n e x p e r i m e n t a l s y s t e m s h a v e i m p l i c a t e d b e h a v i o u r a l i n t e r a c t i o n ( F a u s c h a n d W h i t e 1986; G l o v a 1986; H e a r n a n d K y n a r d 1 9 8 6 ) , d i f f e r e n c e s i n h a b i t a t p r e f e r e n c e ( B u s t a r d a n d N a r v e r 1975; A l l e e 1 9 8 2 ) , o r a c o m b i n a t i o n o f b o t h ( H a r t m a n 1965) a s m e c h a n i s m s p r o m o t i n g d i f f e r e n t i a l h a b i t a t u s e . F i e l d p o p u l a t i o n s h a v e r a r e l y been m a n i p u l a t e d , b u t b e h a v i o u r a l e x c l u s i o n ( H i x o n 1980; F a u s c h and 227 W h i t e 1 9 8 1 ) , s p e c i e s d i f f e r e n c e s i n h a b i t a t p r e f e r e n c e ( E v e r e s t and Chapman 1972; Hume a n d N o r t h c o t e 1 9 8 5 ) , o r b o t h t h e s e f a c t o r s ( E b e r s o l e 1986) a p p a r e n t l y i n f l u e n c e s p e c i e s h a b i t a t u s e i n s y m p a t r y . D i f f e r e n c e s i n h a b i t a t u s e b e t w e e n c o h o a n d c h i n o o k were c o n s i s t e n t b e t w e e n w i l d a n d e x p e r i m e n t a l p o p u l a t i o n s a n d t h e s e s p e c i e s show s i m i l a r d i f f e r e n c e s u n d e r s i m u l a t e d w i n t e r c o n d i t i o n s ( T a y l o r 1 9 8 8 ) . The r e s u l t s f r o m J o n e s C r e e k s u g g e s t t h a t d i f f e r e n c e s i n h a b i t a t u s e b e t w e e n c o h o a n d c h i n o o k a r e l a r g e l y a f u n c t i o n o f d i f f e r e n c e s i n h a b i t a t p r e f e r e n c e w i t h " r e i n f o r c i n g " b e h a v i o u r a l i n t e r a c t i o n b e i n g o f s e c o n d a r y i m p o r t a n c e . Fewer c h i n o o k u s e d p o o l s i n t h e p r e s e n c e o f c o h o t h a n when a l o n e , b u t c h i n o o k were most a b u n d a n t i n r i f f l e s u n d e r a l l c o n d i t i o n s ( T a b l e s 28, 2 9 ) . T h u s , c h i n o o k p r e f e r r e d r i f f l e s , a n d t h e a d d i t i o n o f c o h o a p p e a r e d o n l y t o e n h a n c e t h i s p r e f e r e n c e . P r e f e r e n c e f o r p o o l s by c o h o a p p e a r e d t o be e v e n s t r o n g e r ( F i g . 3 0 ) , b u t t h e i r h a b i t a t u s e i n e x p e r i m e n t a l a l l o p a t r y was n o t t e s t e d . I n sum, c o h o a p p e a r e d t o i n f l u e n c e h a b i t a t u se o f c h i n o o k o n l y i n p o o l s w h i c h a r e a p p a r e n t l y t h e p r e f e r r e d h a b i t a t o f c o h o ( D o l l o f f 1987; B i s s o n e t a l . 1 9 8 8 ) . A t h i r d e x p e c t a t i o n f r o m t h e h y p o t h e s i s t h a t b e h a v i o u r a l i n t e r a c t i o n w i t h c o h o i n f l u e n c e s f r e s h w a t e r r e s i d e n c e by c h i n o o k was t h a t more c h i n o o k w o u l d e m i g r a t e f r o m a s y s t e m i n t h e p r e s e n c e o f c o h o t h a n when a l o n e . W h i l e c h i n o o k e m i g r a t i o n was h i g h e s t i n t h e p r e s e n c e o f c o h o i n J o n e s C r e e k , i t was n o t 228 s i g n i f i c a n t l y d i f f e r e n t f r o m t h e i n c r e a s e i n e m i g r a t i o n c a u s e d by t h e i n c r e a s e i n c h i n o o k d e n s i t y f r o m 1-2/m . The d i f f e r e n t i a l i n f l u e n c e o f c o h o on h a b i t a t u s e by c h i n o o k b e t w e e n h a b i t a t t y p e s may e x p l a i n , i n p a r t , t h e l i m i t e d i n f l u e n c e o f c o h o on e m i g r a t i o n t e n d e n c y by c h i n o o k i n J o n e s C r e e k . M a r k e d d i f f e r e n c e s i n h a b i t a t u s e b e t w e e n t h e s p e c i e s p r o b a b l y l e s s e n t h e e x t e n t o f b e h a v i o u r a l i n t e r a c t i o n a n d h e n c e t h e c h a n c e s o f s o c i a l l y i n d u c e d e m i g r a t i o n . I n a d d i t i o n , w h i l e s t a t i s t i c a l l y i n s i g n i f i c a n t , S l i m a n d E a g l e c h i n o o k may h a v e d i f f e r e d i n t h e i r t e n d e n c y t o e m i g r a t e f r o m t h e e x p e r i m e n t a l s e c t i o n s ( F i g . 32, c_f. J e n k i n s 1 9 7 1 ) . T h i s may h a v e c o m p l i c a t e d d e t e c t i o n o f an e f f e c t o f c o h o on c h i n o o k e s p e c i a l l y s i n c e b e h a v i o u r a l d o m i n a t i o n by c o h o d o e s n o t a p p e a r t o be u n i f o r m among c h i n o o k p o p u l a t i o n s ( F i g . 2 5 ) . D i f f e r e n c e s i n s i z e b e t w e e n i n t r o d u c e d s a l m o n a n d e m i g r a n t s were s m a l l a n d i n s i g n i f i c a n t . S o c i a l s t a t u s a n d r e l a t i v e d o m i n a n c e b e t w e e n i n d i v i d u a l s a r e o f t e n s i z e - d e p e n d e n t (Chapman 1962; A b b o t t e t a l . 1988; P e t r o s k y a n d B j o r n n 1 9 8 8 ) , a n d i f s o c i a l i n t e r a c t i o n s were i m p o r t a n t i n i n f l u e n c i n g e m i g r a t i o n by c h i n o o k t h e n s m a l l e r i n d i v i d u a l s s h o u l d h a v e c h a r a c t e r i z e d t h e e m i g r a n t s . S i n c e t h i s was n o t t h e c a s e some o t h e r f a c t o r p r o b a b l y i n f l u e n c e d e m i g r a t i o n . J e n k i n s ( 1 9 7 1 ) a n d B i l b y a n d B i s s o n ( 1 9 8 7 ) s t u d i e d e m i g r a t i o n i n n e w l y - i n t r o d u c e d , h a t c h e r y r a i s e d r a i n b o w t r o u t a n d c o h o s a l m o n r e s p e c t i v e l y a n d a l s o f o u n d t h a t e m i g r a n t f i s h were n o t n e c e s s a r i l y s m a l l e r t h a n r e s i d e n t s . 229 T h e s e a u t h o r s s u g g e s t e d t h a t i n i t i a l e m i g r a t i o n was due t o f i s h r e s p o n d i n g t o u n f a m i l i a r h a b i t a t s a s w e l l a s t o s o c i a l i n t e r a c t i o n s . D e s p i t e t h e p o s s i b i l i t y o f e m i g r a t i o n i n r e s p o n s e t o u n f a m i l a r h a b i t a t s , t h i s f a c t o r s h o u l d h a v e been c o n s i s t e n t a c r o s s t r e a t m e n t s , y e t more c h i n o o k e m i g r a t e d i n t h e p r e s e n c e o f c o h o t h a n when a l o n e a t c o m p a r a b l e d e n s i t i e s . The p r e f e r e n c e o f c o h o f o r p o o l a r e a s i n t h i s a n d o t h e r s t u d i e s ( H a r t m a n 1965; A l l e e 1982; B i s s o n e t a l . 1 9 8 8 ) , t h e a g g r e s s i v e s u p e r i o r i t y o f c o h o , a nd t h e p r e f e r e n c e f o r r i f f l e s by c h i n o o k p r o b a b l y a c t e d t o g e t h e r when c o h o were i n t r o d u c e d t o ( i ) i n c r e a s e t h e u s e o f r i f f l e s by c h i n o o k a n d ( i i ) i n c r e a s e e m i g r a t i o n by c h i n o o k . T h e s e r e s u l t s a r e c o n s i s t e n t w i t h t h e i d e a t h a t t h e e n e r g e t i c demands o f i n t e r s p e c i f i c i n t e r a c t i o n s c a n be r e d u c e d f o r a b e h a v i o u r a l s u b o r d i n a t e i f i t s e e k s r e f u g e i n a l t e r n a t e h a b i t a t s . S u c h e n e r g e t i c a d v a n t a g e s may r e s u l t i n s e l e c t i o n f a v o u r i n g s p e c i e s s p e c i f i c h a b i t a t p r e f e r e n c e s ( M o r s e 1974; R o s e n z w e i g 1 9 7 4 ) . T h e r e a r e few p r e c e d e n t s f o r t h e s t u d y o f i n t e r s p e c i f i c i n t e r a c t i o n on f r e s h w a t e r r e s i d e n c e t e n d e n c y i n s a l m o n i d s . The d a t a o f S t e i n e t a l . ( 1 9 72) s u g g e s t t h a t a g r e a t e r p e r c e n t a g e o f c h i n o o k e m i g r a t e d f r o m e x p e r i m e n t a l t r o u g h s when s t o c k e d w i t h c o h o t h a n when s t o c k e d a l o n e , a l t h o u g h r e p l i c a t i o n s f o r t h e i r t r e a t m e n t s w h i c h c o n t r o l l e d f o r d e n s i t y d i f f e r e n c e s were t o o few ( 1 - 3 ) t o p e r m i t r i g o r o u s c o n c l u s i o n s . 230 Spaulding et a l . (1988) assessed the i n f l u e n c e of r e l e a s e s of h a t c h e r y - r e a r e d coho on h a b i t a t use, e m i g r a t i o n , and growth r a t e of w i l d chinook salmon in the Wenatchee R i v e r , Washington. These authors observed that coho were more a g g r e s s i v e towards chinook than v i c e versa and that h a b i t a t use, while s i m i l a r immediately a f t e r the coho were r e l e a s e d , was markedly d i f f e r e n t between the s p e c i e s soon t h e r e a f t e r . C o n s i s t e n t with the r e s u l t s from Jones Creek was the o b s e r v a t i o n by Spaulding et a l . (1988) that a much higher percentage of chinook used r i f f l e h a b i t a t s a f t e r coho, which used p o o l s e x t e n s i v e l y , were in t r o d u c e d . By c o n t r a s t to my r e s u l t s from Jones Creek, s h i f t s i n h a b i t a t by Wenatchee chinook were not a s s o c i a t e d with changes i n e m i gration r a t e s . In a d d i t i o n , Spaulding et a l . (1988) found no e f f e c t of i n t r o d u c t i o n of coho on growth r a t e s of r e s i d e n t chinook. Since experimental stream s e c t i o n s were much l a r g e r i n the study by Spaulding et a l . (1988), i t i s p o s s i b l e that s u i t a b l e amounts of u n d e r u t i l i z e d r i f f l e h a b i t a t s were present i n the Wenatchee R i v e r treatment s e c t i o n s to "absorb" chinook d i s p l a c e d from pools a f t e r coho were i n t r o d u c e d . T h i s was probably not the case i n Jones Creek, because even when chinook were Z i n t r o d u c e d alone at 1 fish/m , roughly 40% emigrated. D i r e c t comparison to the study by Spaulding et a l . (1988) i s compromised somewhat s i n c e Wenatchee chinook were w i l d and 231 p r i o r r e s i d e n t s o f t h e s y s t e m w h i l e c o h o were h a t c h e r y - r a i s e d . T h e s e r e s i d e n t c h i n o o k were p r o b a b l y more f a m i l i a r w i t h t h e i r e n v i r o n m e n t t h a n t h e c o h o i n t r o d u c e d i n t o t h e W e n a t c h e e R i v e r o r t h e c h i n o o k i n J o n e s C r e e k . I n a d d i t i o n , p r i o r r e s i d e n t s a r e u s u a l l y f a v o u r e d i n a g g r e s s i v e i n t e r a c t i o n s (Chapman 1962; Mason an d Chapman 1 9 6 5 ) . C o n s e q u e n t l y , t h e p o t e n t i a l f o r c o h o t o i m p a c t upon p r i o r r e s i d e n t c h i n o o k may have b e e n l i m i t e d i n t h e W e n a t c h e e R i v e r s t u d y . S p a u l d i n g e t a l . ( 1 9 8 8 ) , h o w e v e r , c o n c l u d e d t h a t s e g r e g a t i o n o f c o h o i n p o o l s a n d c h i n o o k i n r i f f l e h a b i t a t s r e f l e c t e d g e n e t i c d i f f e r e n c e s i n h a b i t a t p r e f e r e n c e a n d , t o a l e s s e r e x t e n t , b e h a v i o u r a l d o m i n a t i o n by c o h o i n p o o l s . H e a r n a n d K y n a r d ( 1 986) s t u d i e d t h e r e l a t i o n s h i p b e t w e e n r a i n b o w t r o u t (an e x o t i c ) a n d A t l a n t i c s a l m o n i n s t r e a m s o f t h e n o r t h e a s t U.S. I n l a b o r a t o r y s t r e a m c h a n n e l s , r a i n b o w t r o u t t e n d e d t o be more a g g r e s s i v e t h a n s a l m o n and c o u l d d i s p l a c e them f r o m p o o l h a b i t a t s . I n t h e f i e l d , t h e s p e c i e s were f o u n d i n d i f f e r e n t h a b i t a t s , and s t o c k i n g s t r e a m s e c t i o n s w i t h s a l m o n d i d n o t i n c r e a s e e m i g r a t i o n by p r i o r r e s i d e n t t r o u t ( H e a r n a n d K y n a r d 1 9 8 6 ) . H a t c h e r y o r i g i n o f t h e i n t r o d u c e d s a l m o n a n d t h e f a c t t h a t t h e t r o u t were r e s i d e n t i n t h e s t r e a m b e f o r e s a l m o n were i n t r o d u c e d , a g a i n , l i m i t d i r e c t c o m p a r i s o n t o J o n e s C r e e k s t u d i e s . N e v e r t h e l e s s , H e a r n a n d K y n a r d ( 1 9 8 6 ) c o n c l u d e d t h a t h a b i t a t s e g r e g a t i o n b e t w e e n t r o u t a n d A t l a n t i c s a l m o n was l a r g e l y due t o d i f f e r e n c e s i n h a b i t a t p r e f e r e n c e a n d p r o b a b l y o n l y s e c o n d a r i l y t o i n t e r s p e c i f i c a g g r e s s i o n . 232 Comparison of these s t u d i e s with those i n Jones Creek suggests that h a b i t a t d i v e r s i t y i s a major f a c t o r a f f e c t i n g the degree and outcome of i n t e r s p e c i f i c b e h a v i o u r a l i n t e r a c t i o n . The extent of s p e c i e s d i f f e r e n c e s i n h a b i t a t p r e f e r e n c e s and the r e l a t i v e a v a i l a b i l i t y of t h e i r r e s p e c t i v e p r e f e r r e d h a b i t a t s are probably major determinants of the i n f l u e n c e of b e h a v i o u r a l i n t e r a c t i o n on a response such as e m i g r a t i o n . In summary, i n c o n t r i v e d or very simple h a b i t a t s (e.g. l a b o r a t o r y environments), p a r t i c u l a r l y those with p o o l -l i k e c o n d i t i o n s , coho can b e h a v i o u r a l l y exclude chinook and, hence, probably promote emigration from such systems by chinook. By c o n t r a s t , b e h a v i o u r a l i n t e r a c t i o n with coho i n n a t u r a l environments i s probably not a major f a c t o r i n f l u e n c i n g d u r a t i o n of freshwater r e s i d e n c e ( v i a i n t e r a c t i o n f o r h a b i t a t ) s i n c e even i n the r e l a t i v e l y simple environment of Jones Creek coho and chinook s p e c i a l i z e d i n d i f f e r e n t h a b i t a t s . Perhaps i n streams with very l i t t l e o p p o r t u n i t y f o r h a b i t a t s p e c i a l i z a t i o n , or f o r chinook d i s p l a c e d from r i f f l e s by i n t r a s p e c i f i c i n t e r a c t i o n s and attempting to r e s i d e i n pool h a b i t a t s , b e h a v i o u r a l i n t e r a c t i o n with coho may promote a l t e r n a t i v e r e a r i n g p a t t e r n s such as downstream m i g r a t i o n to e s t u a r i n e a r e a s . 233 CHAPTER 4: GENERAL DISCUSSION The f o r e g o i n g s t u d y a d d s t o t h o s e o f R i c h a n d Holmes (1928) and C a r l a n d H e a l e y ( 1 9 84) by p r e s e n t i n g e v i d e n c e t h a t l i f e h i s t o r i e s o f j u v e n i l e c h i n o o k s a l m o n a r e , a t l e a s t i n p a r t , i n h e r i t e d . A d d i t i o n a l l y , t h e d i f f e r e n c e i n t h e t i m i n g o f t h e c h a n g e f r o m f r e s h w a t e r t o e s t u a r i n e a n d m a r i n e r e s i d e n c e i s a s s o c i a t e d w i t h i n h e r i t e d d i f f e r e n c e s i n a s u i t e o f c h a r a c t e r s t h a t a r e c o m p o n e n t s o f f u n c t i o n a l l y i m p o r t a n t " s t r a t e g i e s " f o r a l t e r n a t i v e l i f e h i s t o r i e s ( C h a p t e r 1 ) . T h e s e o b s e r v a t i o n s p r o v i d e e v i d e n c e s u p p o r t i n g t h e h y p o t h e s i s t h a t s t r e a m - a n d o c e a n - t y p e s a l m o n r e p r e s e n t a d a p t i v e d i v e r s i f i c a t i o n , a f e a t u r e t h a t h a s u n d o u b t e b l y been i m p o r t a n t t o t h e C h i n o o k ' s w i d e s p r e a d n a t i v e d i s t r i b u t i o n a n d s u c c e s s f u l c o l o n i z a t i o n a f t e r i n t r o d u c t i o n t o n o n - n a t i v e e n v i r o n m e n t s ( C a r l 1982; F l a i n 1 9 8 3 ) . E n v i r o n m e n t a l m o d u l a t i o n o f " g r o w t h o p p o r t u n i t y " , a n d a b i o t i c f a c t o r s s e l e c t i n g f o r s i z e a n d t i m e o f d o w n s t r e a m m i g r a t i o n were s u g g e s t e d a s i n s t r u m e n t a l t o t h e e v o l u t i o n a n d p r e s e n t g e o g r a p h i c d i s t r i b u t i o n o f a l t e r n a t i v e c h i n o o k l i f e h i s t o r i e s ( C h a p t e r 2 ) . The i n v e s t i g a t i o n o f c o m p e t i t i v e i n t e r a c t i o n s b e t w e e n c o h o a n d c h i n o o k j u v e n i l e s p o i n t e d away f r o m b e h a v i o u r a l d o m i n a t i o n o f c h i n o o k by c o h o a s a b i o t i c e n v i r o n m e n t a l f a c t o r i n f l u e n c i n g c h i n o o k f r e s h w a t e r l i f e h i s t o r y ( C h a p t e r 3 ) . H a b i t a t s p e c i a l i z a t i o n by e a c h s p e c i e s p r o b a b l y m i n i m i z e s t h e p o t e n t i a l f o r c o h o t o i n f l u e n c e d i r e c t l y t h e f r e s h w a t e r r e s i d e n c e by c h i n o o k . T h i s i s c o n s i s t e n t w i t h t h e 234 c o n c l u s i o n s r e a c h e d i n C h a p t e r s 1 a n d 2; v a r i a b i l i t y i n t h e d u r a t i o n o f f r e s h w a t e r r e s i d e n c e i s a t l e a s t p a r t i a l l y g e n e t i c a l l y d e t e r m i n e d . G e n e t i c d i f f e r e n c e s i n h a b i t a t u s e and b e h a v i o u r o f c o h o and c h i n o o k c o u l d s t e m f r o m p a s t s e l e c t i o n f o r h a b i t a t p r e f e r e n c e a s a means o f r e d u c i n g t h e c o s t s o f a g g r e s s i v e i n t e r a c t i o n s . A l t e r n a t i v e l y , s p e c i e s - s p e c i f i c h a b i t a t p r e f e r e n c e s c o u l d h a v e e v o l v e d d u r i n g a l l o p a t r i c d i v e r g e n c e o f c o h o a n d c h i n o o k f r o m a common a n c e s t o r . W h i l e t h e s e a l t e r n a t i v e s c a n n o t be r e s o l v e d , t h e p o s s i b i l i t y o f c o e v o l u t i o n b e t w e e n t h e s e s p e c i e s i s c o n s i s t e n t w i t h r e c e n t i d e a s c o n c e r n i n g t h e d e v e l o p m e n t o f t h e P a c i f i c s a l m o n i d " s p e c i e s f l o c k " . M i l l e r a n d B r a n n o n ( 1 9 8 2 ) p o s t u l a t e d t h a t t h e p r e s e n t d i v e r s i t y o f s a l m o n i d l i f e h i s t o r i e s i n t h e n o r t h P a c i f i c e v o l v e d i n a " c r u c i b l e o f c o m p e t i t i v e a n d e x p l o i t a t i v e i n t e r a c t i o n s " . R o s e n z w e i g ( 1 9 7 8 ) d e v e l o p e d a t h e o r e t i c a l m o d e l o f " c o m p e t i t i v e s p e c i a t i o n " a n d G i b b o n s ( 1979) a p p l i e d a s i m i l a r c o n c e p t t o s y m p a t r i c s p e c i a t i o n i n t h r e e i c h n e u m o n i d f l i e s . I n t h i s m o d e l , i n t r a s p e c i f i c c o m p e t i t i o n p r o m o t e s t h e d i s p e r s a l o f i n d i v i d u a l s t o v a c a n t " i s l a n d n i c h e s " t h a t a r e d i s c r e t e f r o m t h o s e o c c u p i e d by members o f t h e s o u r c e p o p u l a t i o n ( R o s e n z w e i g 1 9 7 8 ) . A d j a c e n t i s l a n d n i c h e s a r e s e p a r a t e d by " d i s r u p t i v e g a p s " s u c h t h a t o f f s p r i n g o f m a t i n g s b e t w e e n o c c u p a n t s o f d i s t i n c t n i c h e s a r e s e l e c t e d a g a i n s t . S e l e c t i o n a g a i n s t h y b r i d s t h e n p r o m o t e s t h e e v o l u t i o n o f r e p r o d u c t i v e i s o l a t i o n b e t w e e n o c c u p a n t s o f s e p a r a t e i s l a n d n i c h e s . M i g h t s u c h a model a p p l y t o 235 d i f f e r e n t i a t i o n w i t h i n c h i n o o k a n d , i n p a r t i c u l a r , t o t h e e v o l u t i o n o f a l t e r n a t i v e l i f e h i s t o r i e s ? The e v o l u t i o n o f a c o m p l e x , anadromous l i f e h i s t o r y i s t h o u g h t t o h a v e been d r i v e n , i n p a r t , by f o o d r e s o u r c e l i m i t a t i o n i n r e l a t i v e l y u n p r o d u c t i v e f r e s h w a t e r s t r e a m e n v i r o n m e n t s ( s e e G r o s s ( 1 9 8 7 ) f o r a r e c e n t d i s c u s s i o n ) . I n t h i s s c e n a r i o , i n d i v i d u a l s a d o p t i n g an a n a d r o m o u s l i f e s t y l e were f a v o u r e d by s e l e c t i o n b e c a u s e t h e a b u n d a n t f o o d r e s o u r c e s i n e s t u a r i n e a n d m a r i n e h a b i t a t s p r o v i d e d t h e o p p o r t u n i t y f o r e n h a n c e d g r o w t h . E c o l o g i c a l l y , a c o n s e q u e n c e o f i n c i p i e n t anadromy was t h a t a n c e s t r a l O n c o r h y n c h u s p o p u l a t i o n s c o u l d r e d u c e n i c h e o v e r l a p by u t i l i z i n g b o t h f r e s h w a t e r a n d e s t u a r i n e / m a r i n e r e a r i n g h a b i t a t s . F u r t h e r s u b d i v i s i o n o f h a b i t a t u s e c o u l d be a c c o m p l i s h e d t h r o u g h d i f f e r e n c e s i n t h e t i m i n g o f t h e s h i f t f r o m f r e s h w a t e r t o e s t u a r i n e / m a r i n e h a b i t a t s . T e m p o r a l n i c h e d i f f e r e n c e s were s u g g e s t e d by C a r o t h e r s a n d J a k s i c ( 1 9 8 4) t o be a c o n s e q u e n c e o f i n t e r f e r e n c e ( a g o n i s t i c ) i n t e r a c t i o n s b e t w e e n s p e c i e s . As w e l l , W i l b u r ( 1 9 8 0) o f f e r e d t h e o p i n i o n t h a t s h i f t s i n t h e t i m i n g o f e v e n t s i n c o m p l e x l i f e c y c l e s i n a m p h i b i a n s a r e o f m a j o r e c o l o g i c a l s i g n i f i c a n c e b e c a u s e t h e y c o n t r i b u t e t o s p e c i e s c o e x i s t e n c e . The f o r e g o i n g d i s c u s s i o n s u g g e s t s t h a t anadromy a n d h e t e r o c h r o n i c c h a n g e s i n t h e t i m i n g o f t h e s m o l t t r a n s f o r m a t i o n c o u l d r e p r e s e n t a l t e r n a t i v e n i c h e i s l a n d s , a s c o n c e p t u a l i z e d by R o s e n z w e i g ( 1 9 7 8 ) , a s t h e b a s i s o f a c o m p e t i t i v e s p e c i a t i o n 236 m o d e l o f d i f f e r e n t i a t i o n w i t h i n O n c o r h y n c h u s . I n f a c t , M c C o r m i c k a n d S a u n d e r s ( 1 9 8 7 ) p r o p o s e d t h a t h e t e r o c h r o n i c c h a n g e s i n h y p o - o s m o r e g u l a t o r y a b i l i t y h ave d r i v e n an e v o l u t i o n a r y t r e n d f r o m s a l i n i t y t o l e r a n c e a t age 1 y e a r o r o l d e r i n c o h o a n d masu s a l m o n ( 0 . masou) t o r a p i d a t t a i n m e n t o f s a l i n i t y t o l e r a n c e a n d s e a w a r d m i g r a t i o n a s n e w l y emerged f r y i n p i n k a n d chum s a l m o n . W i t h i n t h i s scheme, t h e d i v e r s i t y o f j u v e n i l e l i f e h i s t o r i e s i n c h i n o o k may have e v o l v e d a s a " g e n e r a l i s t " p a t t e r n , i n t e r m e d i a t e t o t h e e s t u a r i n e o r i e n t e d e a r l y l i f e h i s t o r i e s o f p i n k a n d chum s a l m o n a n d t h e e x t e n d e d f r e s h w a t e r r e s i d e n c e o f c o h o , s o c k e y e , a nd masu s a l m o n . I n sum, m i c r o e v o l u t i o n a r y d i v e r g e n c e i n d e v e l o p m e n t a l r a t e , d r i v e n by c o m p e t i t i v e i n t e r a c t i o n s , may h a v e p r o m o t e d d i f f e r e n t i a t i o n w i t h i n O n c o r h y n c h u s w h i c h , f o r c h i n o o k , h a s meant t h e e v o l u t i o n o f b o t h s t r e a m - a n d o c e a n - t y p e l i f e h i s t o r i e s . The v a r i a b i l i t y i n j u v e n i l e c h i n o o k l i f e h i s t o r i e s i s a s s o c i a t e d w i t h g e n e t i c d i f f e r e n c e s i n a d u l t s p a w n i n g m i g r a t i o n t i m i n g ( s e e C h a p t e r 2 ) . S t r e a m - a n d o c e a n - t y p e c h i n o o k a l s o a p p e a r t o h a v e d i s t i n c t b e h a v i o u r s a n d d i s t r i b u t i o n s d u r i n g t h e i r o c e a n i c p h a s e s ( H e a l e y 1 9 8 3 ) , d i f f e r e n c e s t h a t may be g e n e t i c i n o r i g i n . S t r e a m - t y p e s a l m o n m i g r a t e f a r a f i e l d n o r t h w e s t e r l y a l o n g t h e N o r t h A m e r i c a c o a s t a n d may move o o f f s h o r e t o a t l e a s t 170 W l o n g i t u d e . O c e a n - t y p e c h i n o o k a r e more l o c a l i z e d ; t h e y s p e n d t h e i r m a r i n e l i f e i n n e a r s h o r e w a t e r s , much c l o s e r t o t h e i r s t r e a m o f o r i g i n . T h e r e a p p e a r s , t h e r e f o r e , t o be a b r o a d d i m o r p h i s m w i t h i n c h i n o o k s a l m o n , b u t 237 i t i s u n c l e a r w h e t h e r t h e d i s t i n c t i o n i s u l t i m a t e l y r o o t e d i n t h e e a r l y l i f e h i s t o r y , t h e t i m i n g o f a d u l t s p a w n i n g m i g r a t i o n , o r t h e m a r i n e m i g r a t i o n s . I n c o n s e q u e n c e t h e r e a r e s e v e r a l ways i n w h i c h i t m i g h t be p o s t u l a t e d t h a t t h e a l t e r n a t i v e j u v e n i l e l i f e h i s t o r i e s c o u l d h a v e e v o l v e d . F o r i n s t a n c e , t h e s y m p a t r i c o c c u r r e n c e o f j u v e n i l e l i f e h i s t o r y t y p e s i n numerous r i v e r s c o u l d h a v e a r i s e n f r o m a l l o p a t r i c d i v e r g e n c e f o l l o w e d by p o s t g l a c i a l c o l o n i z a t i o n . A l t e r n a t i v e l y , s y m p a t r i c l i f e h i s t o r y t y p e s c o u l d be t h e r e s u l t o f i n d e p e n d e n t e v o l u t i o n i n e a c h o f t h e s y s t e m s i n w h i c h t h e y o c c u r . W h i l e an " a l l o p a t r i c d i v e r g e n c e - p o s t g l a c i a l d i s p e r s a l " a r g u m e n t c o u l d e x p l a i n much o f t h e m a c r o g e o g r a p h i c v a r i a t i o n i n j u v e n i l e l i f e h i s t o r i e s ( s e e C h a p t e r 2 ) , t h r e e o b s e r v a t i o n s s u g g e s t , o r a r e a t l e a s t c o n s i s t e n t w i t h t h e i d e a , t h a t s y m p a t r i c d i v e r g e n c e may c o n t r i b u t e t o m i c r o g e o g r a p h i c v a r i a t i o n . F i r s t , t h e r e i s e v i d e n c e t h a t w i t h i n m a j o r r e g i o n s , a n d s o m e t i m e s s i n g l e t r i b u t a r i e s , s t r e a m - a n d o c e a n - t y p e c h i n o o k a r e more s i m i l a r t o e a c h o t h e r e l e c t r o p h o r e t i c a l l y t h a n e i t h e r i s t o c o m p a r a b l e l i f e h i s t o r y t y p e s i n o t h e r r e g i o n s o r r i v e r s ( K r i s t i a n s s o n a n d M c l n t y r e 1976; U t t e r e t a l . 1 9 8 9 ) . I f most o f t h e l o c i e x a m i n e d a r e assumed t o be s e l e c t i v e l y n e u t r a l ( U t t e r e t a l . 1 9 8 7 ) , b i o c h e m i c a l i n f o r m a t i o n a r g u e s t h a t a l t e r n a t i v e l i f e h i s t o r y t y p e s may h a v e a r i s e n i n d e p e n d e n t l y i n s e v e r a l f a u n a l r e g i o n s a l o n g t h e P a c i f i c c o a s t . S e c o n d , i n s o c k e y e 238 s a l m o n , O n c o r h y n c h u s n e r k a , brown t r o u t , Salmo t r u t t a , a n d a r c t i c c h a r r , S a l v e l i n u s a l p i n u s , a nadromous a n d n on-anadromous f o r m s c a n g i v e r i s e t o one a n o t h e r , a n d p r o b a b l y h a v e on numerous o c c a s i o n s ( F o e r s t e r 1947; Behnke 1972; Ryman e t a l . 1979; N o r d e n g 1983; S c o t t 1984; H i n d a r e t a l . 1986; F o o t e e t a l . 1 9 8 9 ) . T h e r e f o r e , o v e r t h e r a n g e s o f t h e s e s p e c i e s , a n a dromous a n d f r e s h w a t e r r e s i d e n t f o r m s p r o b a b l y do n o t r e p r e s e n t d i s t i n c t e v o l u t i o n a r y l i n e a g e s . A s i m i l a r s i t u a t i o n m i g h t e x i s t f o r s t r e a m - a n d o c e a n - t y p e c h i n o o k s a l m o n ; t h e y h a v e p r o b a b l y d i v e r g e d on numerous o c c a s i o n s . T h i r d , s i n c e b o t h s t r e a m - a n d o c e a n - t y p e i n d i v i d u a l s may be p r e s e n t i n p r o g e n y f r o m a p p a r e n t l y s i n g l e b r e e d i n g p o p u l a t i o n s ( e . g . R e i m e r s 1 9 7 3 ) , t h e p o l y m o r p h i s m t h a t w o u l d f o r m t h e b a s i s f o r s y m p a t r i c d i v e r g e n c e e x i s t s w i t h i n p o p u l a t i o n s . I f , i n some a r e a s , s t r e a m - a n d o c e a n - t y p e c h i n o o k d i v e r g e d i n s y m p a t r y two q u e s t i o n s a r i s e : ( i ) what i s t h e m e c h a n i s m o f d i v e r g e n c e a n d how i s i t m a i n t a i n e d ? a n d ( i i ) h a v e o c e a n - t y p e s a l m o n more commonly g i v e n r i s e t o s t r e a m - t y p e c h i n o o k o r v i c e v e r s a ? C e r t a i n a s p e c t s o f t h e e n v i r o n m e n t a n d b e h a v i o u r o f P a c i f i c s a l m o n s u g g e s t t h a t d i s r u p t i v e s e l e c t i o n , i . e . s e l e c t i o n i n f a v o u r o f two o r more modal p h e n o t y p e s ( F u t u y m a 1 9 8 6 ) , may h a v e p r o m o t e d s y m p a t r i c d i v e r g e n c e . F o r i n s t a n c e , H e a l e y ( 1 9 8 3 ) c i t e d s e a s o n a l d i f f e r e n c e s i n a c c e s s i b i l i t y t o s p a w n i n g a r e a s a n d d i f f e r e n c e s i n m i g r a t i o n d i s t a n c e b e t w e e n h e a d w a t e r a n d l o w e r r i v e r t r i b u t a r i e s a s 239 e x a m p l e s o f e n v i r o n m e n t a l h e t e r o g e n e i t y t h a t m i g h t p r o v i d e o p p o r t u n i t y f o r d i f f e r e n t i a l s e l e c t i o n w i t h i n r i v e r s y s t e m s . I n a d d i t i o n , t h e p r e c i s e h o m i n g b e h a v i o u r o f s a l m o n i d s f o r s p a w n i n g p r o v i d e s a m e c h a n i s m f o r r e p r o d u c t i v e i s o l a t i o n b e t w e e n s o u r c e p o p u l a t i o n s a n d d e s c e n d e n t s o f i n d i v i d u a l s t h a t s t r a y e d a n d c o l o n i z e d n e w l y e x p o s e d h a b i t a t s . D i f f e r e n t i a l s e l e c t i o n among h a b i t a t s a n d h a b i t a t s e l e c t i o n d e s c r i b e c o n d i t i o n s where a t l e a s t t h e m a i n t e n a n c e o f g e n e t i c p o l y m o r p h i s m i s most p r o b a b l e ( T hoday a n d Boam 1959; M a y n a r d S m i t h 1962; H e n d r i c k e t a l . 1976; H e n d r i c k 1986) and h a b i t a t s e l e c t i o n d u r i n g r e p r o d u c t i o n i s a c e n t r a l theme i n many c a s e s o f p r o p o s e d s y m p a t r i c d i v e r g e n c e ( K o s s w i g 1963; T a u b e r a n d T a u b e r 1977; McKaye 1980; E c h e l l e a n d K o r n f i e l d 1984; R i c e 1 9 8 5 ) . A f i n a l p o i n t w h i c h s u g g e s t s t h a t c h i n o o k s a l m o n m i g h t d i v e r g e r e p e a t e d l y i n s e p a r a t e r i v e r s y s t e m s i s t h e o b s e r v a t i o n t h a t P a c i f i c s a l m o n d i s p e r s e w i d e l y upon e x p o s u r e t o new h a b i t a t s ( e . g . d u r i n g g l a c i a l r e c e s s i o n ) , e s p e c i a l l y i f s o u r c e p o p u l a t i o n s a r e s m a l l ( Q u i n n a n d F r e s h 1 9 8 4 ) . S u c h r a p i d d i s p e r s a l i s e x e m p l i f i e d by t h e s p r e a d o f c h i n o o k s a l m o n a l o n g t h e e a s t a n d w e s t c o a s t s o f New Z e a l a n d ( F l a i n 1981) a n d t h e r a p i d s p r e a d o f p i n k s a l m o n ( O n c o r h y n c h u s  g o r b u s c h a ) t h r o u g h o u t t h e G r e a t L a k e s ( K w a i n 1987) a f t e r e a c h was i n t r o d u c e d t o t h e s e n o n - n a t i v e e n v i r o n m e n t s . S y m p a t r i c d i v e r g e n c e c o u l d e x p l a i n t h e o r i g i n a n d m a i n t e n a n c e o f a l t e r n a t i v e l i f e h i s t o r y t y p e s w i t h i n s y s t e m s s u c h a s t h e Nanaimo R i v e r . I n t h i s r i v e r , t h r e e s p a t i a l l y a n d g e n e t i c a l l y d i s t i n c t b r e e d i n g p o p u l a t i o n s o f c h i n o o k a r e 240 c h a r a c t e r i z e d by t e m p o r a l d i f f e r e n c e s i n a d u l t s p a w n i n g m i g r a t i o n a n d j u v e n i l e s e a w a r d m i g r a t i o n ( C a r l a n d H e a l e y 1 9 8 4 ) . S e l e c t i v e r e g i m e s p r o b a b l y v a r y among t h e l a k e d o m i n a t e d u p p e r r i v e r , t h e m i d d l e r i v e r , a n d t h e e s t u a r i n e d o m i n a t e d l o w e r r i v e r . As w e l l , m a t u r i n g a d u l t s p r o b a b l y home t o t h e s e a r e a s . T h e s e o b s e r v a t i o n s a r e c o n s i s t e n t w i t h d i v e r s i f y i n g s e l e c t i o n a s a c r e d i b l e h y p o t h e s i s t o a c c o u n t f o r t h e o r i g i n a n d m a i n t e n a n c e of a l t e r n a t i v e l i f e h i s t o r i e s . S i n c e s i m i l a r i l y d i v e r s e e n v i r o n m e n t s a n d d i f f e r e n c e s i n a d u l t a n d j u v e n i l e m i g r a t i o n t i m i n g o c c u r w i t h i n many o t h e r c o a s t a l s t r e a m s i n W a s h i n g t o n , O r e g o n , a n d i n t h e l o w e r C o l u m b i a R i v e r i t seems p r o b a b l e t h a t d i s r u p t i v e s e l e c t i o n may have o c c u r r e d i n d e p e n d e n t l y i n many a r e a s . I f s y m p a t r i c l i f e h i s t o r y t y p e s o f c h i n o o k h a v e a r i s e n t h r o u g h d i s r u p t i v e s e l e c t i o n s i n c e t h e l a s t g l a c i a t i o n ( 1 4,000 y bp o r a b o u t 3,500 g e n e r a t i o n s ) , t h e n c h i n o o k must be c a p a b l e o f r a p i d d i v e r g e n c e . R e c e n t ( w i t h i n t h e l a s t 100 y r ) i n t r o d u c t i o n s o f a n adromous c h i n o o k a n d s o c k e y e s a l m o n t o New Z e a l a n d have r e s u l t e d i n t h e n a t u r a l f o u n d i n g o f f r e s h w a t e r r e s i d e n t p o p u l a t i o n s , some o f w h i c h a r e s y m p a t r i c w i t h a n adromous f i s h ( S t o k e l l 1962; F l a i n 1972, 1982b; S c o t t 1 9 8 4 ) . I n a d d i t i o n , f r o m i n t r o d u c t i o n s o f f a l l - s p a w n i n g c h i n o o k a n d " o d d - y e a r " p i n k s a l m o n t o t h e G r e a t L a k e s , a t l e a s t one s p r i n g s p a w n i n g p o p u l a t i o n o f c h i n o o k ( K w a i n a n d Thomas 1984) a n d s e v e r a l p o p u l a t i o n s o f " e v e n - y e a r " p i n k s a l m o n have d e v e l o p e d . T h e r e i s , f u r t h e r m o r e , e v i d e n c e o f g e n e t i c d i f f e r e n c e s among 241 n a t u r a l i z e d G r e a t L a k e s p i n k s a l m o n p o p u l a t i o n s ( G h a r r e t e t a l . 1 9 8 7 ) , d i v e r g e n c e s t e m m i n g f r o m an i n t r o d u c t i o n o f 21,000 f r y f r o m a s i n g l e d o n o r p o p u l a t i o n i n 13-15 g e n e r a t i o n s . W h i l e t h e d i f f e r e n c e s among t h e p i n k p o p u l a t i o n s a r e s m a l l a n d t h e g e n e t i c b a s i s o f t h e o t h e r l i f e h i s t o r y d i f f e r e n c e s d e s c r i b e d i s unknown, t h e p o s s i b i l i t y t h a t n a t u r a l s e l e c t i o n m i g h t be r e s p o n s i b l e f o r t h e d i f f e r e n c e s s u g g e s t s t h a t r a p i d d i v e r g e n c e w i t h i n O n c o r h y n c h u s s p e c i e s i s p o s s i b l e . The e x i s t e n c e o f s y m p a t r i c i n t r a s p e c i f i c f o r m s i n s a l m o n i d s , a n d o t h e r f i s h e s ( E c h e l l e a n d K o r n f i e l d 1984; M c P h a i l 1 9 8 4 ) , h a s been l i n k e d t o e n v i r o n m e n t a l g r a d i e n t s o r h e t e r o g e n e i t y . F o r i n s t a n c e , F o o t e ( 1 987) s u m m a r i z e d a r g u m e n t s t h a t r e l a t e d t h e s y m p a t r i c o c c u r r e n c e o f i n t r a s p e c i f i c f o r m s i n l a k e w h i t e f i s h ( C o r e g o n u s c l u p e a f o r m i s ) , s o c k e y e s a l m o n a n d k o k a n e e , a n d a r c t i c c h a r r t o f a c t o r s s u c h a s l a k e o r s t r e a m p r o d u c t i v i t y , l a k e m o r p h o m e t r y , a nd p r e s e n c e o r a b s e n c e o f c o m p e t i t o r s . T h i s a p p e a r s t o be t h e c a s e f o r c h i n o o k s a l m o n a s w e l l , s i n c e i t i s i n s t r u c t u r a l l y d i v e r s e , c o a s t a l r i v e r s y s t e m s , where t h e c o s t s o f s e a w a r d m i g r a t i o n p r e s u m a b l y a r e low r e l a t i v e t o u p s t r e a m a r e a s , t h a t s y m p a t r i c s t r e a m - a n d o c e a n -t y p e c h i n o o k a r e most common. D i f f e r e n c e s among g e o g r a p h i c r e g i o n s i n e n v i r o n m e n t a l c o n d i t i o n s f a v o u r a b l e t o d i v e r g e n c e ( e . g . r i v e r l e n g t h , e s t u a r y s i z e ) p r o b a b l y c o n t r i b u t e t o t h e d i s t r i b u t i o n o f s y m p a t r i c l i f e h i s t o r y t y p e s o v e r t h e C h i n o o k ' s r a n g e . 242 Do s t r e a m - t y p e c h i n o o k more commonly g i v e r i s e t o o c e a n -t y p e c h i n o o k , o r m i g h t t h e r e v e r s e d i v e r g e n c e be most common? I f one a c c e p t s t h e h y p o t h e s i s t h a t s a l m o n i d s h a d a f r e s h w a t e r o r i g i n a n d t h a t t a x a h a v e e v o l v e d t o w a r d s r e d u c e d d e p e n d e n c e on t e r r i t o r i a l s t r e a m r e s i d e n c e ( i . e . p i n k , chum a n d s o c k e y e ) T c h e r n a v i n 1939; Behnke 1972; D o r o f e y e v a e t a l . 1981; M i l l e r a n d B r a n n o n 1982; K e n d a l l a n d Behnke 1984; S m i t h a n d S t e a r l e y 1989; b u t s e e T h o r p e 1982) t h e n t h i s m i g h t be i n t e r p r e t e d a s e v i d e n c e t h a t s t r e a m - t y p e c h i n o o k more commonly g i v e r i s e t o o c e a n - t y p e s a l m o n . B o t h Zaugg e t a l . ( 1 9 8 6 ) a n d C l a r k e ( 1 9 8 7 ) r e p o r t e d t h a t s t r e a m - t y p e s a l m o n may s m o l t d u r i n g t h e i r f i r s t y e a r o f l i f e i f t h e i r g r o w t h - o p p o r t u n i t y i s i n c r e a s e d p r i o r t o t h e s p r i n g " m i g r a t i o n window". C l a r k e ( 1 9 8 7 ) , h o w e v e r , was u n a b l e t o m o d i f y t h e g r o w t h a n d s m o l t i n g r a t e s o f o c e a n - t y p e c h i n o o k w h i c h s u g g e s t s t h a t t h e y a r e p h y s i o l o g i c a l l y l e s s f l e x i b l e a n d t h e i r l i f e h i s t o r y i s u n d e r s t r o n g e r g e n e t i c c o n t r o l . P e r h a p s s u c h a p p a r e n t c a n a l i z a t i o n p l a c e s l i m i t s on t h e p o t e n t i a l f o r o c e a n -t y p e c h i n o o k t o g i v e r i s e t o s t r e a m - t y p e s a l m o n . A l t e r n a t i v e l y , r e v e r s a l s o f t h e a p p a r e n t t r e n d t o w a r d s t h e e v o l u t i o n o f more m a r i n e d e p e n d e n t t a x a i n s a l m o n i d s a r e common an d f r e s h w a t e r r e s i d e n t f o r m s o f v a r i o u s s p e c i e s a r e p r o b a b l y d e c e n d e n t s o f s y m p a t r i c a n adromous c o u n t e r p a r t s ( B e h n k e 1972; Ryman 1983; H i n d a r e t a l . 1986; F o o t e e t a l . 1 9 8 9 ) . I n d e e d , o c e a n - t y p e c h i n o o k have g i v e n r i s e t o c h i n o o k w i t h e x t e n d e d 243 f r e s h w a t e r r e s i d e n c e i n New Z e a l a n d w a t e r s ( F l a i n 1979, 1980, 1 9 8 2 b ) . T h e r e f o r e , some s t r e a m - t y p e s a l m o n m i g h t h a v e e v o l v e d f r o m o c e a n - t y p e f i s h f o l l o w i n g t h e l a t t e r ' s u p s t r e a m o r n o r t h w a r d c o l o n i z a t i o n o f n e w l y d e g l a c i a t e d r e g i o n s c o n t a i n i n g h a b i t a t s t h a t s e l e c t e d f o r i n c r e a s e d s i z e a t s m o l t i f i c a t i o n ( a n d h e n c e e x t e n d e d s t r e a m r e s i d e n c e ) . I n h e r i t e d p h e n o t y p i c d i f f e r e n t i a t i o n b e t w e e n s t r e a m - a nd o c e a n - t y p e c h i n o o k ( s e e C h a p t e r 1) s u g g e s t s t h a t t h e r e w o u l d be s e l e c t i o n f o r r e p r o d u c t i v e i s o l a t i o n i n s y m p a t r y . W h i l e t h e l i f e h i s t o r y t y p e s may be s p a t i a l l y s e p a r a t e d d u r i n g s p a w n i n g , t h e r e a r e i n s t a n c e s where s t r e a m - a n d o c e a n - t y p e c h i n o o k spawn i n c l o s e p r o x i m i t y o r where b o t h a r e p r e s e n t i n s i n g l e demes ( F u l t o n 1968; R e i m e r s 1 9 7 3 ) . I n s u c h c a s e s i t i s i n t r i g u i n g t o s p e c u l a t e a b o u t t h e d e g r e e t o w h i c h s u c h s p a w n i n g p o p u l a t i o n s o r l i f e h i s t o r y t y p e s w i t h i n p o p u l a t i o n s m i g h t a l s o be r e p r o d u c t i v e l y i s o l a t e d by b e h a v i o u r a l d i f f e r e n c e s . S t r e a m - a n d o c e a n - t y p e l i f e h i s t o r i e s r e p r e s e n t g e n e t i c a l l y b a s e d , f u n c t i o n a l d i v e r s i f i c a t i o n w i t h i n c h i n o o k s a l m o n . S u c h d i v e r s i f i c a t i o n h a s s u r e l y been i m p o r t a n t i n t h e c o l o n i z a t i o n a n d m a i n t e n a n c e o f p o p u l a t i o n s i n a s p e c i e s w i t h p e r h a p s t h e w i d e s t g e o g r a p h i c r a n g e o f O n c o r h y n c h u s . F i n a l l y , a s f o r o t h e r e x a m p l e s o f l i f e h i s t o r y p o l y m o r p h i s m i n t h e S a l m o n i d a e , i t i s l i k e l y t h a t c h i n o o k l i f e h i s t o r y t y p e s a r e n o t 244 d i s t i n c t e v o l u t i o n a r y l i n e a g e s ; r a t h e r they p r o b a b l y r e s u l t from r e p e a t e d e p i s o d e s of s y m p a t r i c d i v e r g e n c e over much of the n o r t h Pac i f i c . 245 LITERATURE CITED A b b o t t , J . C , R.L. D u n b r a c k , a n d C D . O r r . 1985. The i n t e r a c t i o n o f s i z e a nd e x p e r i e n c e i n d o m i n a n c e r e l a t i o n s h i p s o f j u v e n i l e s t e e l h e a d t r o u t ( S a l m o g a i r d n e r i ) . B e h a v i o u r 9 2 ( 3 / 4 ) : 2 4 1 - 2 5 3 . A l l e e , B.A. 1982. The r o l e o f i n t e r s p e c i f i c c o m p e t i t i o n i n t h e d i s t r i b u t i o n o f s a l m o n i d s i n s t r e a m s , pp. 111-122, I n : E.L. B r a n n o n and E.O. S a l o ~ e d s . J P r o c e e d i n g s o f t h e s a l m o n and t r o u t m i g r a t o r y b e h a v i o r s y m p o s i u m . U n i v e r s i t y o f W a s h i n g t o n P r e s s , S e a t t l e . A l l e n , K.R. 1969. L i m i t a t i o n s on p r o d u c t i o n i n s a l m o n i d p o p u l a t i o n s i n s t r e a m s , pp. 3-20, I_n: T.G. N o r t h c o t e ~ e d . J Symposium on s a l m o n and t r o u t i n s t r e a m s . H.R. 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